When making D&D villains I often start the process by thinking something like "well, I want this dude to be a Half-Dragon Githyanki Beguiler 12". The game mechanics drive the process. While working on my new Star Wars campaign my thoughts have been more along the lines of "I need a bitter jedi that survived the Purge but blamed both the Sith and the antiquated jedi order. In anger he has turned to the Dark Side but is in no way an ally of the Empire or the Sith." Character and setting drive the process instead of mechanics. I'm totally digging that.
"Man, is there anything Jeff CAN'T do when it comes to gaming? This guy is like a critical 20 every roll. Jeff can bite the heads offa five game geeks, including their sorry-ass DM, and spit 'em into a large duffel bag ONE AT A TIME!...that's just the kind of messed up bastard he is! You think yer a gamer, punk? Well..do ya? Jeff will depants your weasel-ass right in front of your grandma."