Probably Wolverine's most defining mutant trait — other than, you know, those razor sharp claws that pop out between his knuckles — is his healing factor. While bullets don't bounce off of Logan's skin, he can heal from any bullet wound in just a few minutes. Stabbings, fire, traumatic head wounds, starvation, diseases... no matter how many times he gets knocked down, he always gets right back up. Wolverine might be nearly invincible, but unlike the Hulk or Superman, he's just as vulnerable as any normal human being. He experiences all the pain that anyone else would, and gets cut up to pieces every other week, but he keeps going, decades passing behind him as he barely ages, slowly outliving everyone he loves.

But in this year's Logan, a film which marks Hugh Jackman's final appearance as the X-Men's resident clawed hothead, we get the rare opportunity to see Wolverine at his most susceptible. Set in a desolate future, age seems to have sapped away at the strength of Logan's healing factor, leaving him tired and weaker than ever before — and no longer quite so immortal.

Since his early days, Wolverine has suffered numerous gory injuries that he would have never survived without his rapid healing abilities. He's also suffered during times in which his healing power was taken away from him, whether by disease or technology. Here are the 15 Times Wolverine REALLY Needed His Healing Factor.

15. His Entire Childhood

With some exceptions, most mutant powers aren't visible in a child's earliest years. Rogue doesn't have any issue with skin contact until high school, when she has her first kiss. Cyclops has perfectly normal eyes until he gets a little bit older. Wolverine's childhood in Alberta is a similarly powerless time, with no claws, no healing, and no pointed hair. Rather than being the tough scrappy kid that one might expect, the child that will one day become the Wolverine is actually weak, sickly, and anemic.

In the years before his healing factor kicked in, the boy — at this time known as James Howlett, not Logan — is frail, and often bedridden. He suffers from allergies so severe that he is rarely able to leave the estate of his wealthy parents without becoming ill. Quite a big difference from the Wolverine we know today.

James's mutant powers finally activate when his father, John Howlett, is killed by the family's groundskeeper, Thomas Logan. Thomas is actually James's birth father, though James doesn't know this at the time. In any case, the shock of seeing John Howlett murdered triggers James's claws to pop out the first time, dripping with blood, which he then uses to kill Thomas Logan. Not long after, the sick little rich boy starts to become the stubborn and unflinching tough guy that we know today, thanks to those claws, enhanced senses, and the ability to recover from any wound in moments. But seriously, he really could have used those healing powers back in the early days; he probably would have had a much happier childhood.

14. The Weapon X Project

From beginning to end, Logan has lived one of the hardest, longest, most painful lives of any character in comics. Sadly, the most traumatic time period of all is the one that has had the biggest impact on his life: the year where he was kidnapped, brainwashed, experimented on, and transformed into Weapon X.

This cold-hearted, inhumane procedure is one that Logan would have never survived without his healing factor. Of course, the downside is that same healing factor is exactly the reason he was chosen for the project. The process of lacing a human being's entire skeleton with hot liquid metal is not only too extreme for any normal person could survive, but also unfathomably painful. On top of that, all that metal that laces Logan's skeleton is constantly poisoning him, meaning that his healing factor has to work nonstop to keep him healthy and well.

Due to his healing factor, the real damage that the Weapon X project did to Wolverine was not physical, but psychological; after having had his mind wiped and his body turned into a weapon, the experiment left him distrustful, paranoid, and without any memory of his past for an enormous chunk of his life.

13. Anytime That He Has Fought Against the Hulk

The Incredible Hulk, who'll be coming back to the cinema later this year in Thor: Ragnarok, is not a dude you want to mess around with. He's capable of sending skyscrapers toppling with a kick, and devastating alien ships in one punch. He calls himself the strongest there is, and he only gets even stronger if you piss him off. Fighting the Hulk is like a one-way ticket to getting crushed beneath that big green foot. But we all know Wolverine, and for better or worse, he's someone who never backs down from a fight, no matter the odds.

Wolverine and the Hulk have a long, storied history together. In fact, Wolverine was actually first introduced in a Hulk comic book, not an X-Men one. Since then, the two of them have swung at one another with claws and green fists on many occasions. While the Hulk usually wins the day, we have to give Logan credit for trying. It takes guts to challenge the Hulk. However, we also have to acknowledge that the only reason Wolverine ever survives his many battles against the Hulk is because of his healing factor, particularly on that one occasion (seen above) when the Hulk actually tears him in half.

Recently, Marvel has been teasing the appearance of some sort of freaky genetic experiment that seems to combine the Hulk and Wolverine into one giant, emerald-skinned, adamantium-clawed hybrid creature. Sounds like a safe idea, right? Can't imagine how that will go wrong...

12. When the Punisher Flattened him with a Steamroller

Hulk isn't the only fellow superhero that Wolverine has gotten himself mixed up with, though calling a murderous vigilante like the Punisher a "hero" is debatable. Though any conflict between Wolverine and the Punisher isn't really a fair fight, since Logan could easily skewer Frank Castle like a shish kabob if he really wanted to, it is true that Frank has somehow managed to deal the X-Men's mascot some pretty serious battle wounds.

Probably one of the silliest interactions between the two occurs in the Punisher's book, when Frank Castle shoots Wolverine's entire face off, leaving just his skull (Why does it take so long for his face to grow back? Who knows). As if that wasn't bad enough, Punisher then shoots him in the crotch, adding insult to injury. Finally realizing that there's no way he can actually stop Wolverine, and wanting the get the X-Man off his back, Castle decides to put him on hold by driving a steamroller right over him, crushing his skull and leaving him there until he's able to squeeze his way out.

Needless to say, this is one instance where Logan's definitely glad that he has a healing factor.

11. When He Marched Up to the Phoenix in X-Men: The Last Stand

The climactic battle of X-Men: The Last Stand, the grand finale of the original X-Men trilogy, occurs when Jean Grey finally begins to let loose. Flames fly around her, oceans shoot up in the sky, and everything she waves her hand at — from soldiers to the X-jet itself — gets reduced to ashes, thanks to her all-powerful ability to decimate the molecular structure of any single object. This easily renders the Phoenix as the most powerful threat the X-Men have ever faced, and anything or anyone that so much as approaches Jean risks being instantly de-atomized. The outlook doesn't look so good.

Except there's one man that could possibly survive her attacks: a man who heals from any wound.

As Wolverine marches toward the Phoenix, his skin is flayed, his costume is torn, his adamantium ribs are exposed, but he keeps healing. It's likely that Jean is holding back, to some extent — but not that much. Jean is way out of control by this point, and by letting him come up to her, Jean allows him to kill her. Regardless of whether Jean really tried to kill him or not, there's no way Wolverine would have survived her attacks if it wasn't for his healing factor.

10.When He Was Turned into A Vampire

One of the most significant times where Wolverine loses his healing factor — only to be saved when the ability kicks back into action, a bit later — is during his brief fling with vampirism. Yes, that's right. Wolverine got bit and turned into a vampire.

The bite is actually delivered by Jubilee, who was previously bit and turned. The vampires use her specifically for the purpose of baiting Logan, so they can get him on their side. You'd think that Wolverine's healing factor would be enough to prevent the disease from overtaking his body, and you'd be right, but there's a catch: as it turns out, before Logan went out to take on the vampires, Cyclops secretly had him injected with a bunch of nanobots that can shut off his healing factor with the press of a button. A button that Cyclops gets to hold, of course. Scott does this so that Wolverine can infiltrate the vampire legion (or put him down, if need be). When the X-Men confront the now-changed Wolverine, Cyclops presses the button again, turning Logan's healing factor back on, and thus ridding him of his vampiric condition.

Sneaky guy, that Cyclops. Never trust him.

9. When Magneto Ripped Out His Adamantium

Oh yeah, this one. Charles Xavier and Magneto might be old pals, but you can bet that Logan's never going to forgive Magneto for this little incident. And really, who can blame him?

Having one's skeleton laced with an indestructible metal is one thing, but when one's greatest enemy just so happens to have magnetic powers, it's not the most convenient characteristic. This unfortunate coincidence makes it easy for Magneto to manipulate Logan's entire body like a puppet, the irony of which has amused Magneto on many occasions. But in the story Fatal Attractions, their connection is taken to its most extreme point -- when Magneto decides to forcibly rip every piece of adamantium out of Wolverine's body. Seriously, it doesn't get much colder than that. Wolverine's gotten knocked around quite a bit, as this list demonstrates, but it's quite possible that this episode may be the most excruciating thing he's ever experienced.

In fact, the pain and recovery of this is so severe that Logan's healing factor actually gets knocked out of commission for a while. While the movie version of Magneto has never gone quite this far, there's at least one instance where he comes pretty close...

8. When Magneto Drowned Him in X-Men: Days of Future Past

There are moments when you wonder if maybe Magneto's not such a bad guy, after all. And then, there are moments where he does something so nasty that you remember that he is, as Logan puts it, an "asshole."

This scene is clearly a tribute to the horrific incident mentioned before, and while not quite as gory, it's certainly just as cruel. It occurs while Magneto is busy trying to kill the president, potentially ruining both the future and the past in one fell swoop. Logan attempts to jump Magneto, but Erik's having one of it. He catches Wolverine in mid-air, grabs metal piping from the ruined stadium around him, and then weaves it in and around his body until Logan is totally unable to move. With the Wolverine rendered helpless before him, Magneto then flings him into the ocean, but not without first taking the chance to mock Logan's prior statement about how both of them are "survivors." Ouch.

As soon as he hits the water, the now metal-interlaced Logan sinks to the bottom, and starts drowning... and drowning... and drowning. His healing factor keeps him alive (which seems to contradict comic book canon a bit), but in the most awful way possible. Stuck at the bottom, he has no way of escaping, no way of freeing himself until he's finally fished up sometime later.

7. When the Hulk Ate Him

Clearly, Wolverine just can't get a break. Even in all of these post-apocalyptic futures, he still gets brutalized in crazy extreme fashions that no one else ever has to go through.

We already mentioned the Hulk earlier on, but this particular sequence happened in the alternate reality of Old Man Logan, and it's gruesome enough that it earns its own entry. In Old Man Logan, Bruce Banner has become a supervillainous landlord who rules over Hulkland, a territory that has replaced the West Coast. After Banner orders to have Logan's family killed — as you can tell, this particular incarnation of Hulk is quite different from the one we're used to  — Wolvie is understandably upset, and he tracks down the big green guy for revenge. The two engage in a final battle, which ends when the Hulk actually eats Logan. Yes, eats him. He bites, chews, and swallows him alive. It's just as bizarre as it sounds.

But thanks to his good ol' healing factor, Logan survives the depths of the Hulk's gamma-irradiated digestive system. He pops his claws, tears the Hulk open, and slashes his way to freedom, slaying the beast once and for all.

6. When Nitro Burned All His Skin and Flesh Off

Just in case you thought that the whole Punisher head-shot incident was the only time Wolverine's been blown away down to the bones, here's one time he had an even harder recovery. Nitro is a villain whose whole M.O. involves blowing himself up, and then regenerating moments afterward. Sort of similar to Wolverine, in that sense, except a lot more catastrophic. As one might imagine, this means that Nitro tends to leave a pretty devastating path of destruction in his wake. In the comics, it is actually a battle with Nitro that leads to the superhero Civil War, when one of his infamous blowouts leaves 600 dead.

In any case, Wolverine tracks Nitro down shortly afterward. Makes sense, really. When you want to stop a guy who blows himself up, send the guy who always regenerates, right? Sure enough, as soon as Logan and a bunch of agents track Nitro down, the villain does blow up, just as expected. Unfortunately, this explosion kills all of the agents, and leaves Logan as nothing more than an adamantium skeleton.

But this is Wolverine we're talking about, so he fully regenerates just in time to deliver Nitro the beating of his life.

5. When He Got Shot by Carbonadium Bullets

Adamantium is Marvel's miracle metal. While it might not have the unique, vibration-absorbing properties of vibranium, Marvel's second most famous fictitious metal, there's nothing as unbreakable as adamantium. So it's no wonder that many scientists have attempted to replicate its properties, with one of the more dangerous results being a new metal called carbonadium.

The scary thing about carbonadium is that it is actually poisonous to mutant healing factors, meaning that if someone like Wolverine, Sabretooth, or Deadpool gets shot by carbonadium bullets or impaled by a carbonadium knife, the power of their healing factors will be severely dampened. This makes the metal one of the most effective weapons in the world if one wants to have a chance against Logan, and he's faced carbonadium bullets on multiple occasions. Luckily, the carbonadium seems to only be truly effective while it is still in the bloodstream; upon removal, the healing factor rapidly gets back to work and repairs the damage.

4. When He Survived a Nuclear Bomb in the Comics

Wolverine's been on the edge of death hundreds of times, facing injuries and mutilations that almost no one else on the planet could possibly survive. But at the most extreme end of the spectrum, his healing factor actually proved strong enough to save his life when a nuclear bomb was dropped right on top of him.

Yes, really.

This crazy incident occurred in Venom #9, not too long after the Venom symbiote makes an unsuccessful bid to bond with Logan. Well, okay, it's not actually the true Venom symbiote, but that's a long story we won't get into. What matters here is that Wolverine finds himself in one hell of a messy conspiracy, and his stopover in the little Canadian town of Voici hits a bit of a snag when a nuclear bomb is dropped on the town. Goodbye, Voici. Wolverine survives the whole thing due to his healing factor, which can be explained, even if it's a bit of a stretch. The harder explanation is how his pants and boots survive, even though the rest of the town is reduced to dust. As far as that goes, we don't have any answers. Of course, this wouldn't be the last time that we see Wolverine surviving a nuke...

3. When He Survived a Nuclear Bomb in the Movies

When it comes to crazy opening scenes, it's hard to top the first few minutes of The Wolverine, which was director James Mangold's first stab at the immortal mutant. Here, it's revealed that all the way back in 1945, Wolverine was a prisoner of war near Nagasaki, Japan, being kept at the bottom of a special armored cell deep underground. Since this happened to be at the end of WWII, it means that Logan was there right in time for the United States to drop the first atomic bombs on both Nagasaki and Hiroshima, meaning Wolverine ends up right in the middle of the blast radius.

As the alarms go off, the Japanese soldiers allow their American prisoners to escape, and one private named Ichiro Yashida decides to free Logan from captivity. However, when he opens the cell door, Logan tells him that there's no point in running away, and tells Yashida he should come down with him if he wants to have a chance at surviving. Yashida ends up doing so, and Logan uses his body to shield him from the atomic blast — though not without sustaining quite a bit of damage.

2. His Death

With the advance notice that Logan will mark Hugh Jackman's final appearance as Wolverine, and the rumors flying that the cinematic version of the character might finally meet his end, it's worth looking back on the final moments of the comic book character, as well. Not surprisingly, this death scene is not a moment where Logan was lucky to have his healing factor; in fact, the whole thing occurs because a virus has stolen his healing powers away from him, leaving him just as human and vulnerable as anyone else. He just needed it now more than ever.

Wolverine's death in the comics occurs when he tracks down Dr. Abraham Cornelius, the immoral scientist responsible for transforming him into Weapon X all those years ago. Seeing that Cornelius wants to conduct even more brutal human experiments on innocent test subjects, Logan slashes open the doctor's adamantium containers, covering his body with molten adamantium. Though the metal starts hardening, Wolverine has just enough time to successfully kill Dr. Cornelius. But with no healing factor to save him, he begins suffocating within his rapidly-cooling adamantium shell. He spends his last moments walking into the sunset, as the metal fully hardens around him, knowing that he has at least stopped the man who caused him so much pain — and thus prevented the doctor from ever conducting similar experiments on anyone else.

R.I.P. Logan. You did good.

1. Every Single Time That He Pops His Claws

Remember that scene back in the first X-Men movie, when Rogue asks Wolverine if it hurts when the claws come out? Sure enough, his response is "every time."

And well, yeah. It should hurt. He's releasing three super-sharp knives from each hand, each claw stabbing right through the flesh, tendon, and muscle on its way out. The only reason that his hands aren't dripping with blood every time is because the wounds heal before any blood can escape. If he didn't heal so fast, he'd probably die from severe blood loss. Not to mention, those between-the-knuckle wounds would never have a chance to heal on a normal person, because those aforementioned adamantium knives would keep ripping them open over and over again.

But it gets even worse. Wolverine doesn't show a lot of discrimination when it comes to what he slashes his claws on, you know. Cars, metal doors, people, monsters, anything that threatens him or his loved ones. But that means his claws are highly susceptible to infection, especially with all the warm bodies they've stabbed into. When they slide back into his arms, those infections slide right inside Logan's body. Once again, lucky that he has a healing factor.

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Were there any other times when Wolverine depended on his healing factor for his very survival? What other death blows has he made it through alive? Let us know in the comments!