Why was he a bad guy. Why did he want to kill the Jedi? Overall, what was his motive. I never understood what it was but I may have missed it. Can somebody explain?

@moywar700: Palpatine groomed him preety much into the role ( Maul was given to him as an infant by his mother). His motive was simply to follow his masters teachings and perhaps one day repalce huim like most sith.

@moywar700: This might be of some help. (I wrote it awhile ago and I'm too lazy to summarize :D )

http://www.ugo.com/tv/star-wars-the-clone-wars-darth-maul-facts

You could check out his page on Wookieepedia for more info as well.

I think maul's motive in the movies was basically to do the bidding of palpatine. But i personally think that he himself had some kind of hidden secret about his hate of Jedi. If you want to know some more about him, check on the page warkiller suggested, and also read the book Darth Maul Shadow Hunter