(SPOILER) One form of Sephiroth requires more than four players to fight.

But really I like having a complete roster of spells. I missed getting Trine on the first play through (I'm sure many people did). That was nothing compared to the frustration of Pandora's Box. I've been playing FFVII off and on for years fighting scores of Dragon Zombies, trying every trick to get it to cast PB. A week ago I read of a theory that DZ *only* casts it the first time you fight it. Now they tell me.

Anyways I have a mania for completeness and closure. Nothing bothers me more than loose ends.