Let me say this: I hate comic books where superheroes will kill henchmen but not supervillains. I'm reading Mark Millar's Ultimate X-Men, and in one scene Storm stops Wolverine from intentionally killing a Big Bad Guy, even thoughWolverine unintentionally killed a Little Bad Guy only moments before (the kind of Little Bad Guy who appears for so few panels, it's obvious he's just there to get killed). If you're the type of hero who fights crime in such a reckless fashion that your battles cause collateral damage, then you might as well just kill everyone. The X-Men—in Millar's story anyhow—are only allowed to kill people accidentally. It's obvious that the reason they don't kill supervillains is because then the story would be over and writers would have to create new supervillains.
If you have knives on your hands, or lasers for eyes, and you're fighting people, THEY ARE GOING TO DIE.