I was surprised no one had mentionned him yet. The fact that you need to set up three well-balanced parties to tackle him (and therefore use most of FFVI's large cast of characters) has always made him stand out as one of the best final boss I have played.AmberSword said:Wait I just noticed that in my first post I forgot Kefka... I FORGOT FRIGGIN KEFKA.
The mad god is my favourite boss of all time in the FF series, at the rate Square Enix (used to be Squaresoft) is going I doubt they're capable of doing anything to top that now.
BG2: Kangaxx the Demi Lich
OOO-moded Oblivion has many great and extremely hard boss fights.
The best is probably Lord Volmyr, the Vampire Lord in Nornalhost. He is almost always invisible (casting detect life helps, but you cannot read his prompts and block him effectively), extremely fast and will disarm you with almost every hit. Moreover, he is surrounded by at least half a dozen Vampire Patriarch/Matriarch. Each of them would qualify as a boss in its own right.