michigami
normally, the knee-jerk is to say sephiroth for me, but i've had to deal with worse bosses.
my personal favorite? Kefka. No particular reason. ya just gotta love a psycho clown boy with wings and horrible fashion sense for going nuclear on the world, and looking damn scary doing it.
whee Well, I love sephiroth to bits. dont'get me wrong.. but for the reason of hte boss fight? i mean, his music rocks.. and his super nova was beyond greatness.. but as a fight overall.. I mean.. i managed to beat him.. and I didn't have any of the following: W2 summon, mime, knights of the round, W2item.... now.. those are all significant materias as they provide unstoppable attacks... and.. somehow i managed to do it (just barely, but still)... I didn't consider him the best -boss- fight. I just liked sephiroth.
moving on to what i really wanted to quote you for.... KEFKA, that slimey bas... omg. i hated him. that first time you fight him when he has all those soldiers in the underworld area... i have till this day never figured out to trick to getting passed it before all my guys die. and kefka wastes all my people... one day i'll manage to surpass it and finish rest of the game. and in my opinion.. not only is kefka a damn hard boss -fight-.. but he is overall one of the top villans in all FF games ever hands down. He is just complete evil down to the core and likes it that way. He just didn't try to take over the world. he tried to go beyond that.