Are we talking only comic books here, or all forms of fiction?
Because, as far as I know, comic books are pretty much the only medium where murdering people automatically makes one a villain.
James Bond and Indiana Jones are heroes who cheerfully shoot bad guys in the face, the average good guy in the average American action movie has a bigger body count than a mafioso, even the kids in Avatar The Last Airbender (except Aang, who is practically Jesus) killed a lot of Fire Nation soldiers (surely plenty of soldiers didn't survive the fall of the dirigibles) and were determined to kill the Fire Lord (they only relented when they saw that he got a Fate Worse Than Death).