There is a difference between Superhero comic book characters and the kinds of characters found in more traditional storytelling.  The difference is that comic book characters are infinitely malleable.  There is no limit to the degree to which comic book characters can have things happen to them that may negatively impact their character.  But there is always the possibility, if required by the author, that these negative changes can be reversed. 

Almost everything that is external to the character can change, be destroyed, and subsequently be restored.  This is most obvious in the comic book trope, Not Really Dead, where a character is actually killed in a particular storyline, only to re-appear later and their completely fine.  And it is up to the pleasure of the writer as to whether we get an elaborate explanation of their resurrection or if it is simply passed off without comment.

What cannot change, however, is their style and attitude.  Deadpool or Ironman are both irreverent, wisecracking, anti-authoritarian heroes, and this attitude is as much a part of their character as the more narrative sense in which characters are developed.

Traditional characters are developed through the events that happen to them throughout their lives, and the choices they make when presented with these crises.  For a comic book character, these choices almost don't matter, unless they are necessary to the plot.