A few characters from my D&D campaign:
Revenge -- duh
General sense of anger at the world (the illegitimate son of a king, who became an evil mercenary to act out his aggression)
Moral differences -- a Lawful Neutral cleric who believed that the LG clerics were failing to keep the proper order, and that logically, removing them was the only way to keep things safe and secure. The needs of the many, after all...
Lack of understanding that people are people -- Cthulhu-esque monsters that saw people as trinkets, toys, devices, but were polite and moral with each other.
Fear -- a Lawful Evil wizard who fights demons and devils, defends the innocent, but has gotten so caught up in the royal politics that he has lost sight of his earlier goals. He now acts primarily to protect his own interests and keep his position in court secure -- so that he can keep doing "good"... He'll summon a devil and send it to kill the PCs because "They're trying to get rid of him."
Loyalty -- the LN lieutenant of a LE wizard who fights because the wizard, who saved him from a life of slavery, asks him to do so.