I just did a story where a mainstream villain was killed in a fairly intense way. I'm personally of a mind that there can be no real suspense in a story arc where you know everything is going to end fine and everyone is going to make it in one piece. Since the start of my story, I've had two main characters injured, a villain long-term incapacitated, and now a villain executed in the name of suspense.
I'd like to get people's opinions on this style of fan fic writing within a comic book setting. I know from reading blogs and forums elsewhere that there is no consensus on whether it's cool or not to kill major characters. I haven't done that yet but it has crossed my mind in previous forays into writing. I'm not going to cite core canon as proof positive that this is cool. Reason number one, Marvel is turning major characters into Disney princesses (see Thor and Wolverine) Reason number two, the infamous rape story arc in Ms Marvel/Captain Marvel's background that led to her refusing to affiliate with SHIELD going forward. Reason number three, Superman has done plenty of things that everyone agreed weren't cool himself in his very long history that I won't list and I'm not as familiar with DC as I am Marvel to specifically cite.
So ultimately, most of us agree that you have to have real consequences in your story to have real drama and suspense especially in crime fiction,etc. But when is it acceptable to have character killing and how far is too far? Obviously you don't kill your main characters, but where does the line of taboo begin?