Quote Originally Posted by NeoCracker View Post
Ultimecia - She wanted to rule everything at once. Power Hungry Dictator wannabe.
She wanted to have control over time, and by consequence, over her own fate. Everything Ulti did, was because she didn't want to die by the hands of the legendary SeeD. That was her fate.

Yu-yevon - Um, I don't know. I can't even remember why this guy did anything he did.
From what I remember, he was just like a "machine", doing what he was "programed" to do. He didn't have any consience of his own actions.