Thanks for entering Shinymist! I agree with you wholeheartedly. It is the character of a person or creature that makes a villain. The scariest ones are the ones you can't see coming.
(Cont.) They would also be smart in their way of being villainous, have a plan rather than just destroy everything in their path without a care. The best villains are the smart ones with purpose behind their villainy, the ones with either a backstory to back them up or a giant ego. Whoever the villain is, they must be intelligent. Claws and black robes and white skin could most definitely contribute to their evilness, though. But it's the character itself that makes the villain, to me.
My ideal villainous humanoids might not have to be big and scary with pointy teeth and sharp claws, or be beautiful and luring, or even be sadistic. It doesn't matter to me what they look like. They would just have to be extremely egoistic and motivated in whatever they are doing for whatever reason they are doing it. They could just be generally harmless creatures unless you provoke them, such as human beings for the most part. As long as they are doing it for a reason. (Cont.)