There are not many characters left on the island who have never killed anyone to our knowledge. Let's see...
Claire, unless her mother has since died, and in any case a car accident is hardly the same as murder... (Desmond better watch his back when he returns sans Charlie, though; she knows about their psychic connection, and he just may find himself punctured by a cradle some moment when he's not watching. No, I don't seriously think she'll go after him, but she'll be spitting nails that he allowed it to happen, in a tearful rage a la the first season finale...)
Rose. If she kills someone... Man, she better not. Hurley was quite bad enough.
Vincent. Though it was rather classless of him to deprive poor Roger of his arm. Which eventually led to Hurley's killing of Ryan... No. I'm not playing that game. Plus, Vincent tried to save Nikki. In vain. And we all cried forever.
Steve. As far as we know. Same goes for Neil, Sullivan and any other random castaways we have hanging around, plus Zack, Emma, Cindy and several random Other folks. Have Alex and Karl killed anyone? I'm thinking no?
Walt. He's sorta still around I guess, and innocent unless we can pin Naomi's death on him somewhat... But I'm thinking we'll just let John shoulder the blame for that. I really doubt his message went: "You have work to do. I need you to kill that nice lady with the phone."
I seriously don't want all these people in prison if/when they get rescued. But somebody needs to figure out some way of curbing everyone's murderous streaks.