Re: Sasuke's hidden motive: is he good or bad
I dont really think he is evil in the traditional sense. A real bad person wouldnt go to such lengths as flat out defying Oro to spare the lives of his would be victims. That fact alone qualifies him in some degree to be considered still good at heart. When he said he now could and would kill Naruto at a whim, I think he was lying to himself as well as the team. Id agree that he wanted to leave the message to just leave him alone.
However, turning his back on Konoha and his friends is the act of a betrayer. Expecially considering where he went to. Turning to someone as evil as Orochimaru clearly shows that he doesnt care about good or evil anymore. The problem with Sasuke is that his mind has been bent by his single motivating goal of revenge.
Vengeance is a primitive motive based on hatred and anger. He has let that hatred consume him to the point that he has developed a sense of values that walks a gray line between real good and evil.