The Bad Guys: Ulterior Motive

Every story, whether it be a book or movie, needs a villain . And every villain needs an ulterior motive. Why? Because then... the villain has no purpose. He's just someone who wears a cape and yells, "MWHAHAHAHAHA!".
So today we'll talk about what makes the bad guy bad. Why they rob banks and become serial killers. Once you know why they do wrong, you'll be able to write your own villain who has depth and meaning.

Here's a list of fairly well known bad guys (or gals) I'd like to use as examples:

BoneMan
Cruella DeVil
Darth Vader
Sauron
Ixion eh Haref
Butch Cassidy
Satan
The average bully

Greed/Money: Butch Cassidy. He loved money, therefore he robbed banks. That's kind of simple one, and probably the easiest trait to put in a character.

Jealousy: Cruella DeVil and Satan could be put under this. Cruella was jealous of the dalmatian's spotted fur and wanted it so she could have a spotted coat. She was a little wacky, if you ask me.
Satan. He's jealous of God. He wants people to worship him like they love and worship the Lord.
Sauron is, in the beginning, also jealous of Iluvitar. (here's were you get your Tolkien allegory)

Revenge: Ixion eh Haref, my own creation. He wanted to exact revenge from his father for killing his mother, and after he tastes blood and power, he begins to lust for it and wants to then rule the world, so he can be put under "Power/World Domination" too.

Power/World Domination: Probably the most common trait of a villain. Sauron, Satan, Ixion, and Darth Vader all go under this one, for obvious reasons.

Religion: Darth Vader, well, sort of. Darth Vader has been seduced by the power of the Dark Side of the Force (basically Lucas' weird evil, the Force is sort of a religion that all things are controlled by an unseen force that lives within things, much like Asian beliefs.)

Twisted Reasons: BoneMan. He thinks he's the perfect father, and he wants the perfect daughter. He abducts young women and when they don't measure up to his standards, he breaks their bones and leaves them to die.

Another one whom I don't have a person for is Mental Problems. The people who aren't all there, which causes them to kill, among other things.

Problems at Home: the reason accredited to most of your average bullies. They don't have such a great life, so they need something to take out their anger and hate on.

These are some of the main things that cause people to do wrong, and can be the perfect basis for your bad guy.