Bah, Sephiroth...probably the most disappointing final boss in the history of Final Fantasy. His only rival is Necron from FF9 in that Necron was just this random thing that fit nowhere into the story line whatsoever.
Never mind Sephiroth himself; I always found that supernova whatever attack that he had to be the lamest and dumbest attack ever in any game that has been created.
"oh look here comes a meteor it crashed into the sun and now for no particular reason the sun has gone supernova and now it has burnt the entire freaking earth to a crisp which means that everyone is now dead
lol j/k it did 1000 damage and the world is fine
and he can also do this attack again"
Yeah, that is another dumb thing about that battle. For starters, why screw around summoning meteor when he could have just wiped out the entire universe with Supernova? Would have saved me a hell of a lot of time.
Though, I am not sure if he can do it again. I think it drains too much of his MP to cast it again, which is sad given how lame a move it is (it's not even real damage, it's percentage based...meaning that it can't kill you). The reason I say this is that I have never seen him cast it twice, though once I accidentally used a Megalixer on him and sure enough he casted it again.