A strawman – few are claiming that killing is admirable. But it is sometimes justifiable or necessary.Killing is the lazy, stupid way to solve things. Any animal or falling rock or large body of water can kill -- it's nothing to praise or admire.
See, there's that moral equivalence I was warning about. The actions of a serial killer are NOT equivalent to that killer being executed. The motivation, method and result are distinctly different.The morality of refusing to kill is not about judging other people's goodness, it's about not losing our own. I despise the argument that if someone else does something bad, that entitles you to turn off your ethics and do the same bad thing to them.
But if your argument is valid, let's extend it – if killing is wrong, then so is assault and deprivation of liberty. Batman is wrong for punching bad guys, and the state is wrong for putting those guys in jail.
You talk about avoiding moral compromise, but accepting assault and imprisonment of criminals is, by your argument, also a moral compromise. And if you say, "Ah, but it's acceptable in context, because it's a lesser harm to prevent a greater harm," well, that's my argument too.
The harmless hero is a good thing in children's entertainment, but it's a fantasy adults should not entertain in a serious way. Unlike genre fiction, reality doesn't provide handy plot twists and gimmicks so the hero doesn't have to sully his hands. When bad people are doing bad things, usually the only thing that will stop them is force, which is sometimes deadly.And superheroes are supposed to be aspirational figures. They're supposed to represent the best of human potential. No, not all of them -- there's room for flawed heroes or antiheroes in fiction -- but many of them, certainly. Superheroes represent hope, and if every single one of them is unable to find an alternative to killing or doesn't even try, that's just cynical and depressing. I grew up in the '70s and '80s with TV heroes who refused to take life, or who at least regretted it when they were unable to avoid it.