Practically any super hero, EVER.
Why? The way you make money of comic books, you have to keep 'em rolling out of the press. And people do not like having a new villain with shitty powers and personality to be introduced and killed off in every comic book, so there are fan favorites...
And you get hundreds, or more likely thousands of super heroes who fail to contain super villains. Super villains who have no problem with killing people, and who end up killing a lot of innocent bystanders, policemen, and everything. Most comic books only show the struggle between the apparent hero and the apparent villain. They don't bother with details. It's all about personal victories, and not the actual benefit of people who the superhero should be protecting...
How many times has Joker or Scarecrow escaped the prison/insane asylum/ et cetera? Plenty. How many casualties they inflicted? Plenty. How hard would it be for Batman, or the police, or any other superhero to kill them off after they've shown that prison doesn't hold them? Not very hard at all, considering that they got caught and apprehended plenty of times. Of course, killing 'em off would only last a few issues because nobody dies in comic book world forever aside from Peter Pan's uncle or whoever the fuck he is... But, y'know. Practicality.
I'm not a comic book nerd because I have little appreciation for most generic "heroic" stories, but I've read a few. The only real heroes are heroes that come from finite series that don't have to last practically forever.