Just the sheer notion of a "supervillain" is inherently terrifying: imagine, in the real world, if a morally twisted megalomaniac, a serial killer, or an alien monster decided to start blowing up cities. Whether it's Thanos trying to reshape the entirety of reality with the Infinity Gauntlet, or a lunatic mass murderer like Carnage getting bonded to a powerful alien life form, comic books — and comic book movies — are filled with stories of near-extinction, catastrophes, and massive property damage.

Luckily, these villains are usually stopped by Earth's many, many superheroes. But what if the heroes had one bad day... and became villains?

Consider, for a moment, just how powerful, brilliant, or influential some of our favorite superheroes are, and imagine if they had no moral compass. Arguably, many of the most popular superheroes out there would be a thousand times more potentially destructive (or just flat-out creepy) than the villains we know, and so here are 15 Superheroes Who Would be Absolutely Terrifying if They Became Villains.

15. Hulk

Marvel Comics Hulk Alternate Version Maestro

Yeah, so, if the Hulk went nuts? Goodbye, world.

Seriously, it's hard to imagine many things more potentially catastrophic than an evil Hulk. Sure, the Hulk we do know has often caused some pretty severe property damage in his rampages, but that's more incidental: he's either trying to defend himself from military attacks, or looking to take down a bad guy. However, just imagine if the Hulk truly became a villain — an unstoppable monster that only became stronger the angrier he got.

For an example of what would happen if the Hulk went evil, take a look at the comic storyline "Future Imperfect," which introduced a bearded version of the Hulk from an alternate future who called himself the Maestro, and decided to take on the world. Needless to say, the world didn't survive him too well. Let's hope evil Hulk never happens in the regular Marvel Universe, or it's toast.

14. Storm

Storm Avengers

Ororo Munroe, AKA Storm, is easily one of the most powerful X-Men out there. There's a good reason that she was, at one point, worshiped as a goddess. Being able to control the weather itself is no small feat. Luckily, Storm has a strong moral compass, and incredible leadership capabilities. But what if she switched sides?

The only thing that "limits" Storm's ability to control the weather is that she doesn't want to endanger innocent lives. If that ceased to be a concern, she could easily create tornadoes, blizzards, hurricanes, or any manner of potentially catastrophic weather patterns, at any time, and wipe out entire towns in mere minutes. There'd be no way to take her on, as anyone that opposed her could be easily swept away. Seriously, as a villain, Storm would be almost unstoppable.

13. Ant-Man

The idea of describing Ant-Man as "terrifying" might sound weird, we know. Yes, he's the guy that shrinks. That's what he does. But seriously, hear us out for a second.

Imagine the sort of creepy, disgusting damage that Ant-Man could do if he were a murderous supervillain. He could shrink down, wriggle his way into someone's ear, nose, or throat, and cause serious damage to their internal organs — without them ever even realizing that he was the perpetrator. People would be coughing up blood, dying, never having any idea that Ant-Man had killed them.

He also could transform into Giant-Man, of course, and crush a few skyscrapers. But the damage he could do in microscopic form would certainly be a lot more nightmarish.

12. Batman

Batman

As far as mainstream superheroes go, Batman is already about as scary as a hero can get without kinda being a villain. He dresses up like an animal that regular people have nightmares about, is a master of martial arts, a genius detective, and has a massive hoard of wealth that can buy him any new gadget or technology he wants. Luckily, he's on our side, so he applies all of these skills to the cause of fighting crime in Gotham City.

But what if, one day, Bruce Wayne had a change of heart... and decided he instead wanted to be Gotham's kingpin?

Really, it's hard to imagine that anyone out there could stop him from becoming the top mob boss. The only reason that all of Batman's villains are still alive, particularly the Joker, is because Bruce is so against killing. If you were to take Batman's morals away, he'd be the most horrifying thing in all of Gotham City by a long shot.

11. Black Panther

Now, think about everything that makes Batman such a potentially terrifying villain, multiply it by a thousand, and you get T'Challa. While Batman is cold and calculated, the Black Panther — even as a hero — is absolutely ruthless.

While Batman may be a billionaire, T'Challa is the king of an entire advanced nation. Like any world leader, T'Challa must always walk a fine line when it comes to issues of morality, diplomacy, and maintaining his nations's affairs, and this can often be a struggle; however, anything or anyone that threatens Wakanda fully knows his wrath.

But imagine if Black Panther went all Doctor Doom, and decided to expand his rule to include the entire world? Keep in mind, Wakanda is probably the single most technologically advanced nation on the planet — and unlike Doom, who enforces his domination over Latveria with authoritarian rule, T'Challa is truly beloved by his subjects. If T'Challa stormed the United Nations with all of the forces of Wakanda behind him, it's hard to imagine that the Avengers could stop him.

10. Teenage Mutant Ninja Turtles

Creepy Teenage Mutant Ninja Turtles

Okay, so the Ninja Turtles probably wouldn't be able to destroy the world, or anything like that. But the reason for their entry on this list is that if they weren't the cuddly, pizza-loving heroes in a half-shell that we know, they'd actually be like something out of a horror movie.

Honestly, think about it.  These are four uncomfortably humanoid turtle mutants, who live in one of the dingiest, least hygienic places imaginable — the sewers of New York City  — and occasionally lurch up to the surface according to the commands of a man-sized rat. Now, because the Turtles are saving lives, we give them a pass... but what if instead, they were coming up onto the streets in order to prey on the city's citizens? What if they crept out of the sewers, brought people down below, and ate them? Needless to say, they'd definitely be some of the creepiest baddies around.

9. Scarlet Witch

Scarlet Witch Marvel Avengers

The unpredictable, chaotic, and intensely powerful nature of Wanda's abilities already make her an inherently risky member of the Avengers, so just imagine how much worse it would get if she went full-on villain. Wanda has already had her share of villainous incidents — such as House of M, or the whole moral inversion trick she performed that actually made heroes like Iron Man into villains, and people like Carnage into heroes — but these events tend to be more accidental, as the result of painful traumas, or due to Wanda being manipulated by others (usually).

But if Wanda became a true villain, then we'd be looking at a foe that manipulates the very nature of reality itself. She could change the world with the snap of her fingers, wipe people out of existence, manipulate the fabric of the universe, and any current supervillains out there (save for maybe Thanos) would look like small potatoes by comparison.

8. Spectre

The Spectre - Underrated DC Superheroes Who Deserve Their Own Movie

Similarly to the Scarlet Witch, the deceased-and-resurrected Detective Jim Corrigan — better known as the Spectre — is a figure of immense power with very few limitations. Spectre is the spirit of God's vengeance, charged with punishing the world's guilty, wielding limitless abilities to reshape reality, manipulate time and space, change matter, and basically do anything that he wants to. On top of that, since he's already dead, Corrigan is practically invulnerable, unless his opponent is an especially powerful magic user.

That's already pretty unsettling, but let's say that the Spectre were to become a villain. What if he used his powers for the forces of evil? It's hard to imagine that the Justice League would have any chance of stopping him.

7. Martian Manhunter

Martian Manhunter begins to transform into multiple versions of the character

J'Onn J'Onnz, the Martian Manhunter, is one of those superheroes who is a lot more powerful than he lets on. While he possesses such abilities as telepathy and telekinesis, the primary power that could make him absolutely terrifying would be his complete control over his entire molecular structure.

Basically, Martian Manhunter can transform himself to resemble anyone, or change the density of his matter to move through any surface, becoming more solid, gain mass, lose mass, and so on. While this gives him the ability to disguise himself as other people, it also has a lot of other horrifying possibilities: basically, any monster that you can dream up, J'Onn can alter his body to transform into. Now, he can do this anyway, but if J'Onn weren't the noble hero that we know him to be — and if he were instead a hostile villain — then the possible beasts he might mold into could be like something out of Hellraiser.

6. Mr. Fantastic

Evil Reed Richards Mr. Fantastic doppelganger Marvel

There are a lot of high-IQ geniuses in the Marvel Universe, from Tony Stark to Henry Pym. But arguably no one is even close to being as inventive and brilliant as Reed Richards, the leader of the Fantastic Four, a guy who creates world-changing technologies on a daily basis, regularly travels to the Negative Zone, and can do just about anything except cure his friend Ben Grimm of his rocky condition.

Doctor Doom may be smart, but despite all of his resources and intelligent, he would have no chance whatsoever against an immoral, villainous Reed Richards, a man who doesn't suffer from Doom's insecurities, and whom infamously corrected the Latverian dictator's flawed theorizing when both of them were younger, much to Doom's chagrin.

On top of that, Mr. Fantastic's rubbery powers could also be taken to some horrifying lengths, if he were to cut loose. He could kill people in ways that we'd rather not think about.

5. Black Bolt

Black Bolt

The fearsome leader of the Inhumans is Blackagar Boltagon (yep, that's really his name), better known as Black Bolt, a man known for one incredibly distinctive feature: he never talks. There's a reason for that, however. The second that Black Bolt opens his mouth and starts to speak, he emits a sonic scream that can destroy walls, shatter entire cities, demolish people's skeletons, and basically destroy anything within its path. Even so much as a whisper or a cough is enough to cause massive property destruction, so Black Bolt must constantly stay focused, and in control.

Now, if Black Bolt were a villain? If anyone got in his way, all he would have to do is sneeze, blow out a little air, and his opponent would no longer exist. If he decided to scream, he could flatten entire civilizations in mere seconds.

4. Wolverine

Wolverine's bloody claws

Wolverine might be one of the good guys, but that famous temper of his already scares a lot of his X-Men teammates from time to time. Seriously, there's a reason that so many villainous organizations are always itching to turn this poor guy into a brainwashed weapon. He's almost immortal, possessing the ability to rapidly heal from just about any wound. His enhanced senses enable him to track a target down from miles away. He has an unbreakable skeleton, and as if that weren't enough, he has six unbreakable claws to go with it, which can skewer anything from a ribcage to a steel door.

Wolverine has been used and abused by more villains than he can count, always trying to manipulate his killer instincts to their own ends. If there's ever a guy you'd want on your team, it's him... and he's also the guy you would never, ever want going up against you.

3. Ghost Rider

Ghost Rider's Johnny Blaze in the Marvel comics

The Spirit of Vengeance is already about this close to being a villain, as it is; while Johnny Blaze has struggled to steer the Ghost Rider toward helping people, the problem is that the Rider himself is actually a demon named Zarathos, and that demon's intentions are certainly far, far away from being virtuous.

Don't be fooled by the fact that Ghost Rider tends to stick to smaller scale situations. This guy could take on the Hulk, and it'd probably be a somewhat fair match. On top of that, Ghost Rider also possesses the Penance Stare, his ultimate ability, which forces a person to relive the pain of every person they've ever hurt. While this power certainly has a much more paralyzing effect on villains who have performed many grievous injuries to others, it could also hurt regular people (and even heroes) pretty dramatically.

2. Charles Xavier

Professor Charles Xavier X-Men

Magneto is incredibly powerful, but don't be fooled: the only reason that he and Charles Xavier are on equal footing, as far as powers go, is because of Xavier's morals. Though Charles has certainly had his share of less than savory moments, as a whole, he strives to use his powers for good, and to not needlessly destroy other people's lives. If Xavier were to become a villain, there would be absolutely no stopping him.

With Cerebro (or Cerebra), Xavier has access to the minds of every single human being on the planet. He has the power to freeze them in place, to block or restructure memories, to paralyze people, to change their entire personality. He could make anyone into his follower, his slave, and they'd never even realize it. If Xavier had been the X-Men's adversary rather than their leader/founder/mentor, then the poor team of mutants would have probably never had a chance.

1. Superman

Superman kills the Joker in Injustice

And of course, when it comes to heroes who we really, really don't want to see turn to the dark side, the top of the list has to be the most famous of them all. Superman has always been an icon of truth and justice, and due to his boy scout nature, it's sometimes easy to overlook how much he's constantly holding back. The only reason Batman can ever beat Superman is because Superman's such a nice guy; if Kal-El wanted to, he could destroy Batman with a flick of his finger. If he were to be fully unleashed, there's almost no force on Earth that could truly stand in his way.

For an example of what happens when Superman becomes the bad guy, see the comic book storyline Injustice, which shows a Man of Steel brought to the breaking point, whereupon he decides to take charge and inflict his authoritarian rule over the entire planet. The sheer contradiction of seeing an inherently hopeful character like Kal-El go evil is exactly what makes the story so terrifying. No doubt about it, if Superman were the villain, he'd be the scariest comic book baddie of all time.

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What other heroes would be horrifying if they became villains? Let us know in the comments!