Episode 2 spoiler from the comic version....
.... Really, don't read if your not ready for spoilers.
After finding his mother dying killed by Tuskan Raiders, he goes on a ramage and kills the raiders, I wouldn't really consider it an evil act. In fact I've been known to base CG DND characters around things like that, but in George Lucas world it's evil.
It's not the killing the Jedi consider evil, Luke killed thousand by blowing up the death star. But they were evil you say, well, the Tuskan Raiders have never been depicted as anything other then evil, it's the anger that's what makes him evil. I don't buy it, but that's Lucas.
End Spoiler