Jecht FFX, Personally my favorite evil dude because he looks soo badass and the music just fit that battle, unless u call Seymore a main boss, then I guess he ranks #2 from FFX

On FF, Garland (Duh, because he is soo badass, haha)

FFVI Kefka, I love his laugh, haha, its awesome, even tho that game is old, it is amazing

VII Sephi isnt, Sipher Sephi was fun, and whatever the first form was, that was fun too

XI Havent beaten it yet

XIII So far as of chapter 11 I think Barthandolus (However you spell his name) is pretty interesting, I havent died on him yet, haha, I still have yet to fight him again though.