if they like causing pain, (emotional, mental, or physical) that sometimes makes them even worse. especially if they're the type of villain who finds out a person's mental or emotional weakness and then exploits it ruthlessly. especially if they do it in such a way that their victim doesn't know what's happening, the victim might even like the villain, and the villain might be kind to the victim. the villain would gain the trust of the victim, then use that trust to undermine the victim's security, sense of self, ego, life, whatever. that sort of thing makes the villain a bit creepy and really really hateable