Deadpool
From: Marvel Comics
The Merc with a Mouth is likely one of the most famous superheroes in the world right now. Interestingly, Deadpool was really sort of separated from other mutants in the X-Men universe initially. This is likely due to his mercenary status. Wade Wilson was part of the armed forces and acted sort of as a mercenary for hire before finding out he had severe cancer. Willing to do anything to remove it, he joins up with an organization that gives him the super-power of regenerative healing. It is actually far more advanced than the healing factor other characters like Wolverine are known to have. Wade can have his entire head sliced off and it’ll either grow back or can be reattached. In fact, Wade only needs a microscopic portion of himself to be present in order to regenerate entirely.
Yet the cancer cells are equally unable to die, meaning he keeps his cancer but it simply cannot kill him. Thus, they take over his body to disfigure him. They’ll always regenerate with everything else. Cancer in his brain actually causes him to be slightly crazy, which is why he’ll often talk to himself or to others that are not there. That allows him to “break the 4th wall” for readers, as we are essentially one of the things not “truly there.” Naturally, Deadpool is one of the best comic book antiheroes, because he is certainly fine ending lives. He’ll even torture people to get information and do whatever he must to achieve his goal or finish his mission. Yet he does not just end people to end them, no matter how nuts he is. He usually has a purpose for it that most can understand.