The infinite boss rush combined with "we'll go into an animation any time you're doing well to make sure that you lose your ATB charges and limit breaks as often as possible" as a hell of a way to design an endgame.
"We like the end of the game to be completely different from the 40 hours that came before so the player is dramatically unprepared. It's like two games in one!" -- Nomura, probably
I might have to put this one down for a few weeks.