While a well-maintained comic storyline that stretches over years of issues and brings a plethora of fascinating characters together is always great, sometimes you just can't beat a good "What If?" story. These one-off tales of wonder and intrigue may not be officially recognized as part of the Marvel cannon (which, let's face it, is a pretty loose concept in the first place), but when done well, they manage to serve the always important function of putting comic fans' most elaborate speculative scenarios into the pages of an actual Marvel comic. And, of course, they help keep things fresh.

In fact, sometimes the comic itself doesn't even have to be that great. Some "What If?" scenarios are so compelling in their own right that the simple pleasure of watching the scenario unfold before your eyes is more rewarding than even the greatest Marvel releases. The mere whisper of these questions is enough to send the imagination of comic book fans into overdrive, and they remain some of the most intriguing concepts of all.

Here are the 15 Best Marvel "What If?" Storylines Of All Time.

15. What if Professor X of the X-Men had become the Juggernaut?

Professor X and The Juggernaut Marvel

In case you aren’t up to speed on your X-Men lore, the premise of this one will probably strike you as particularly absurd. See, Charles Xavier and his stepbrother Cain Marko were once out in Korea on assignment when Marko just so happened to find the Temple of Cyttorak. Upon taking hold of the Gem of Cyttorak (Cyttorak was big on branding), Marko was granted the power of the Juggernaut, which also so happened to cause a collapse that left him (presumably) dead. As you likely know, that was not the case.

This brilliant piece of alternative history sees Marko and Xavier switch roles. In this version, Xavier accidentally touches the Gem of Cyttorak and finds himself going all Juggernaut in the process. Meanwhile, Marko escapes but is filled with resentment over the power that Xavier denied him. This is where things get interesting. See, Marko doesn’t take Xavier’s place and form a pro-mutant party. In fact, nobody does, and Magneto pretty much becomes the sole voice for mutants everywhere. Xavier (as Juggernaut) crushes Magneto’s party and proves to be an unstoppable force of violence. At the end of the day, Juggernaut is launched into space and Cyclops vows to form a resistance against Magneto, who is now positioned to be the next Juggernaut-type power in the universe.

14. What if The Punisher Was a Hall Monitor?

Marvel The Punisher Frank Castle Spinoff

Every now and then, these “What If?” comics decide to just throw out all logic and embrace comedic absurdity. The results of this approach can often be…well, let’s generously call them “underdeveloped.” The basic problem with these comedy premises is that they rarely prove to have the mileage necessary to get a full comic out of what is, essentially, a one line joke. There are certainly good intentions behind them, but the execution leaves a lot to be desired.

Leave it to Frank Castle, then, to master the execution of a “What If?” comedy story. To be clear, “What If The Punisher Were a Hall Monitor” isn’t exactly a comedic masterpiece that has been lost to time. It is, fundamentally, a childish and silly narrative built around an absurd premise like most other comedy “What If?” tales. However, it’s impossible to not love this story of what would happen if The Punisher were suddenly made hall monitor of a school of super students if for no other reason than it so happens to be a source for some of the greatest out of context panels in Marvel history. The premise is intriguing, and the product largely delivers on its comedic potential.

13. What if the Avengers Defeated Everybody?

What If The Avengers Had Defeated Everyone

Wait, by everybody, does this comic mean…everybody?

Yup. Well, mostly. While innocent civilians and animals are presumably left to roam the Earth, the basic idea here is that The Avengers have vanquished every major villain and superhero in the world. This is actually a play on an earlier comic involving the Scarlet Centurion that sees the Centurion lure The Avengers into defeating every other superhuman in order to prevent the apocalypse. Some multi-verse shenanigans occur and, ultimately, everything ends up going back pretty much to the way it was.

In this version of the story, that whole “back to the way it was” bit is scrapped in favor of seeing what would happen to the world if The Avengers were the only superhero force left. This is where the story draws some controversy. While some of the ideas included in the aftermath are fascinating (The Hulk permanently reverts back into Bruce Banner, the world is arguably much safer, etc.) at the end of the tale it ultimately comes down to The Scarlet Centurion vs. The Avengers. Though The Avengers are initially defeated, Thor is able to demolish Centurion and save the day. It’s a slightly convenient ending to an otherwise fascinating premise.

12. What If the Fantastic Four had not gained their super powers?

Fantastic Four space travel

Your initial reaction to this premise would probably be to answer “Well, they wouldn’t be the Fantastic Four now would they?” but before you jump to that conclusion, consider the exact set-up. See, instead of simply having the Fantastic Four embark on their infamous space mission and skip over the receiving their powers bit, in this version, Reed Richards and crew decide to delay the entire mission in order to secure more funding. In fact, when the mission is attempted again much later, it’s now a trained crew of astronauts that embark upon the quest and are successful in helping Earth establish several galactic colonies.

From there, things start to get dicey. Reed and the rest of the group use their immense wealth to establish an intergalactic research facility while a giant monster starts to ravage Earth. Feeling a sense of obligation, the not-so-fantastic four decide to take on this foe with their mere human abilities. The basic philosophy here is that these four were always going to be heroes, regardless of whether or not they actually had their abilities. Besides a few clever callbacks to the powers they would have had, they are able to save the day with little more than their wits and ingenuity.

11. What if Beast and the Thing continued to mutate?

Beast's transformation over the years in Marvel Comics.

Beast and The Thing are two of Marvel’s most tragic creations, in the sense that both were promising young men in the prime of their lives before a series of circumstances robbed them of their lives, potential and humanity. Ignoring the political ramifications of mutation that are always present in the Marvel Universe, the mutation of these two men was cruel if for no other reason than it robbed them of any possible chance to live a semi-normal life. As much as these men can relate to each other over their shared circumstances, however, it turns out that if they had continued to mutate, things would have gone very differently for each of them.

The Thing’s continuing mutation does eventually lead to him becoming a radioactive monster (who looks and sounds a lot like The Incredible Hulk) as you might expect. However, The Thing continues to mutate to such insane degrees that he actually reaches a point of “critical mass” and his mutation just kind of destroys itself. As a result, he can now live as a normal man. Beast is not so lucky. He just gradually morphs into a cannibalistic monster and is exiled to the savage land in order to live with the dinosaurs. Can’t win 'em all, we suppose.

10. What if Wolverine Had Killed the Hulk?

What if Wolverine Had Killed the Hulk

Anyone that has ever read a comic that sees Wolverine and The Incredible Hulk go mano y mano knows that it usually results in a pretty epic fight that typically ends with The Incredible Hulk coming out on top (usually by ripping Wolverine apart). As advertised, this tale simply argues that Wolverine is the one to come win the battle this time. Initially, this doesn’t really seem to have much of an impact beyond giving Wolverine an impressive new notch in his combat belt. However, as in most “What If?” stories, the devil is in the details.

Now that Wolverine has defeated one of the most powerful entities that Earth has ever known, he starts to develop something of an ego problem (more than usual, we mean). This eventually leads to him developing an even shorter temper, which in turn results in him killing some poor fool in a bar fight. Now an outlaw, Wolverine decides to join Magneto’s Brotherhood. His first assignment is to infiltrate the X-Men, which is going along quite nicely until Wolverine falls in love with Jean Grey (as tends to be the case). Eventually, Wolverine repents his evil ways and he and Magneto kill each other in their resulting brawl.

9. What if Venom Had Possessed The Punisher?

Venom symbiote Spider-Man villain

For a brief time, the Marvel writers became obsessed with the idea of what would happen if Venom took over other Marvel heroes. It’s an intriguing concept that more often than not led to said hero becoming corrupted and evil. So it goes.

The one very interesting exception to this rule is the time that Frank Castle was invaded by the Venom symbiote. At first, things go about the way that you’d expect. Castle is invaded by the alien, gets a sweet new outfit and goes a little crazy. What’s truly fascinating about this instance, however, is that Frank Castle actually starts to take a measure of control over the symbiote. He learns to maximize its potential and use his newfound abilities to enact a much more violent war on crime. Keep in mind that this is long before Frank Castle was written to be a more violent vigilante, and that this was really the first time that Marvel fans got a taste of what that would look like.

Even when the suit does eventually consume Castle, he is still able to fight off its effects via a trip inside his own mind that sees him literally hunt down his inner demons in the jungle. From start to finish, this is one of those rare examples of a “What If?” premise that capitalizes off of its fascinating concept and delivers an equally compelling story.

8. What if the Hulk Had Always Had Bruce Banner's Brain?

Bruce Banner Hulk Transform

The Incredible Hulk is one of the most dangerous creatures to ever grace the pages of Marvel Comics. He is a being of immeasurable strength that can withstand a barrage of fire from the world’s military and come away with his purple shorts remarkably intact. In fact, most circumstances that involve The Incredible Hulk being defeated are often so elaborate that they may as well be “What If?” scenarios. However, for as powerful as The Incredible Hulk is, it’s important to remember that it’s often his unhinged rage that makes him so incredibly dangerous.

So what happens if you remove that rage? What happens if The Incredible Hulk retains the brain and mentality of Bruce Banner? According to this comic, quite a bit. Not only does Bruce Banner marry Betty Ross with her father’s blessing, but he lives a pretty normal life outside of that whole “transforming into The Hulk at night” thing. However, without The Incredible Hulk as we know him, Loki is never able to send him against Thor, and The Avengers never form because of it. Instead, Banner actually forms a superteam of his own that cures Benn Grimm of his radiation disease, recruits Professor X (who never forms the X-Men) and eventually defeats Galactus via a monstrosity known as the X-Man, who in turn transfers his powers to a now Hulk-like Benn Grimm.

7. What if someone else besides Spider-Man had been bitten by the radioactive spider?

What if someone else besides Spider-Man had been bitten by the radioactive spider

Given the whole, “With great power comes great responsibility” saying, it’s always been implied that had anyone else besides Peter Parker been granted the abilities of Spider-Man (and if the circumstances that surrounded Parker never happened) things could have gone pretty wrong. Most fans have always assumed that this would instantly translate to someone using said powers to become renowned supervillains, but this collection of stories puts a twist on that theory by showcasing what would have happened if Flash Thompson, Betty Brant, and John Jameson had been bitten by the radioactive spider.

None of them become a villain, exactly, but each one does prove to be incapable of shouldering their awesome new responsibility. Flash kills a man in a wrestling ring and becomes a fugitive that never fully develops his web-slinging abilities. Because of this, he is easily defeated by the Vulture in his first real encounter. Betty Brant becomes terrified of her newfound abilities and decides to quit the life after Uncle Ben is murdered by a thief she couldn’t stop. As for John Jameson, his father actually decided to spin his powers in the papers in order to make him a bonafide American hero. Sadly, he lacks Parker’s intelligence, and is killed trying to stop a shuttle from crashing into the Earth. Interestingly, every story still ends with Parker using the body of the radioactive spider to develop the abilities for himself.

6. What if Cable had destroyed the X-Men?/What if Magneto took over the U.S.A.?

Cable art X-Men Marvel

Admittedly, this is a bit of a cheat considering that it is a two-part series, but the premise is far too fascinating to ignore.

What those titles essentially translate into is “What if the X-Men had lost?” Specifically, this story involves Cable using a bomb to kill Cyclops, Jean Grey and Professor Xavier. Because of this event, the X-Men are left to just kind of wander aimlessly now that their leaders are gone. In fact, the only people who are able to really make any sense out of this chaos are Magneto and Wolverine. Wolverine forms a loose coalition of heroic mutants while Magneto takes this opportunity to seize control of the American government.

From here, things begin to spiral out of control. The Sentinels are formed in response to this mutant uprising and are actually successful in destroying the majority of mutants via some nuclear attacks. Because of this, Wolverine loses what is left of his fragile mind and forms a loose group of fairly weak mutants who roam the apocalyptic world looking for redemption. It’s a pretty depressing read across the board.

5. What if Wolverine battled Conan the Barbarian?

Conan Comics 4 Spider

Oh boy, where to begin?

First, yes they do mean the actual Conan the Barbarian.  Now, you might be thinking that there isn’t possibly any good reason that Conan and Wolverine would have to be in the same universe, much less fighting each other. You’d be right, too. The basic idea here is that Wolverine falls into an alternate reality while touring the Watcher’s base during that whole Dark Phoenix saga. This universe so happens to be the one populated by Wolverine and Red Sonja, and Wolverine so happens to stumble upon Red Sonja and develop a bit of a thing for her, since she looks like Jean Grey. Because of this, Conan beat the hell out of him and leaves him for dead.

Here’s where things get weird. Wolverine regresses to savagery and hunts down Conan. In the process, a mystic opens a door to Wolverine’s reality and offers him the chance to go back. However, due to fight-related circumstances, it’s actually Conan that falls into the portal. The wild Conan begins to fight the entirety of the world’s mutants and even takes out Cyclops after Conan confuses Jean Grey for Red Sonja. This leads to Dark Phoenix running unchecked and consuming the Earth. As for Wolverine, he settles for a new life as Red Sonja’s lover.

4. What if Spider-Man Had Never Become A Crimefighter?

Otto Octavius/Peter Parker as the Superior Spider-Man in Marvel Comics.

We’ve already seen what would happen if Peter Parker hadn’t been the one to initially acquire the powers of Spider-Man, but this comic answers the even more intriguing question of what would have happened if Peter Parker decided that whole crime fighting thing wasn’t for him. Would he turn to a life of crime? Withdraw himself from society? Continue his professional wrestling career?

Actually, according to this issue, he would become a fame-hungry celebrity. See, after stopping the burglar that would have gone on to kill Uncle Ben, Spider-Man discovers that he can easily parlay his abilities into a promising film career. It’s not long before Spider-Man is dominating national airwaves and marketing campaigns. Soon thereafter, he even decides to start a public relations firm designed to increase public awareness and perception of fellow superheroes.

Eventually though, the fame game goes to Parker’s head, and he starts to push his weight around a little too much. This is especially true of J. Jonah Jameson who really hates this diva version of Spider-Man and concocts an elaborate plan to take him down. The plan is foiled by Daredevil, whom Spider-Man offers a part in his next movie. One thing leads to another and, before you know it, Daredevil is beaten half to death, Spider-Man reveals J. Jonah as the ultimate villain, and Peter Parker starts to understand the concept of responsibility.

3. What if Captain America Were Revived Today?

Captain America's shield broken in Secret Wars comic

So, as you may know, Captain America gets frozen once upon a time and is only thawed out when Namor the Sub-Mariner stumbles upon him. Captain returns to the world, inspires truth and justice, beats up some bad guys and makes sure that superheroes enjoy a healthy run of keeping America safe from evil.

That doesn’t happen in this comic. In this version of the story, Steve Rogers isn’t discovered until 1983. This late wake-up call may not have been that impactful on the fortunes of America were it not for the fact that a soldier decides to revive a false version of Captain America and Bucky that he believes to be the real deals. As it turns out, this version of Captain America isn’t quite as morally noble as the real one. This fake Captain becomes obsessed with the idea of protecting America from communism and begins to help support a series of policies that turn America into an isolated police state that the real Captain America even temporarily confuses for Nazi Germany when he is brought back into the world.

At this point, Steve Rogers joins an underground resistance led by Nick Fury, J. Jonah Jameson, and a gun-toting Spider-Man. Together, they are able to take America back and begin the healing process.

2. What if the Avengers had become pawns of Korvac?

What if the Avengers had become pawns of Korvac

In 1982 (in publishing terms) The Avengers faced one of their greatest threats yet when they took on the entity known as Korvac. This powerful being was able to master energy itself via a computer module and used his abilities to destroy a great number of Avengers. Eventually, Korvac becomes disheartened after he feels that his love (Carina, who you may remember from Guardians of the Galaxy) has betrayed him, and he abandons his attempts at total domination.

The twist here is that Korvac never becomes disheartened. Instead, his love doubles down on her affections for Korvac and inspires him to complete his mission. Now, what’s interesting about this is that the comic plays off of the implication that Korvac believed his intentions were good. As such, he starts to enact a series of moves designed to make his universe a safer place to live. The problem is that these moves include blocking the Gods from interfering, banishing powerful superheroes, forming his own band of evil Avengers and trying to kill The Watcher. That last one proves to be a particularly bad decision that inspires The Watcher to form an incredibly formidable group of galactic powers designed to take down Korvac once and for all.

When that fails (it should be noted that Korvac is insanely strong at this point), eventually just about every known power in the universe decides to form together and kill Korvac. Unfortunately for them, Korvac decides to use a little device known as the Ultimate Nullifier in response to this injustice that so happens to destroy the entire universe in the process. That’s a shame.

1. What If the Avengers Fought the Kree-Skrull War Without Rick Jones?

The Avengers and the Kree-Skrull War

Brace yourselves, because this one is a doozy.

Right, so way back in 1980, Marvel published an Avengers issue that saw Rick Jones get caught up in an ongoing war between the Kree Empire and the Skrulls. Kree Supreme Intelligence actually ends up capturing Rick Jones and using his incredible mental powers to defeat the Skrulls and win the war. Everyone pats each other on the back, has a couple of beers, and goes home.

The alternative version of this is not so simple. In this version, Ronan the Accuser kills Rick Jones before he can be used as a tool to win the war. Because of this, the Skrulls gain a considerable advantage and begin to point nuclear weapons at Earth. Never one to let such a thing go unpunished, Professor Xavier decides to unite the entirety of the Marvel Universe (heroes and villains) against the Skrull invasion. Everyone from Doctor Doom to Daredevil begins to fight the Skrulls, making this one of Marvel's earliest major crossover events. Incredibly, even this is not enough to stop the Skrulls outright. Instead, that only occurs when the Skrull Emperor’s daughter stages a coup and forces the Skrulls to embrace more peaceful ways. If ever a “What If?” story was begging for a movie, this would be the one.

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What's your favorite "What If?" storyline from Marvel Comics? Sound off in the comments.