before he became a villian. 
why was he such an interesting character? 
why is he your favorite character ? 
i wanna learn more about him as a character. what trades should i pick up to start? 

He's not my favorite character. I began to dislike him after Messiah CompleX when he turned villain.

He started out as a good guy. But, from what I hear, he was always meant to be a bad guy. From the future, in love, in his own way, with Xavier's dream, and determined to protect it by "any means necessary." A guy like that could be very dangerous, and or very loyal. He acts as if the fate of the future rests in his every move. The embodiment of "Desperate men do desperate things in desperate situations". He is a very serious character. Personally, I think he suffers from PTSD. Whatever happened to him in the future, it was not a happy time. Anything he can do to prevent that future he came from, he will do it, with no hesitation. If he is out to get you, you better hope you got someone like Cable with you. Otherwise... 
 
Look into Age of Apocalypse Alpha, and AoA Omega.