* although I haven’t fought Omega Weapon yet (somehow) but that’s the only one
** or likely even its regular Attack – I remember on my first playthrough 1-shotting the "Final Aeon" with Anima’s reg Attack on the 1st turn of the round, accidentally, hoping to just wear it down, & being disappointed at not having a fight
EDIT:
Ahhh, I now understand why you may think Anima is a game-breaker. The boss I’ve mentioned is only in the PAL and International versions of the game – look at its stats, pretty much impossible to get it killed in one hit, without Zanmato. (http://finalfantasy.wikia.com/wiki/Penance_%28Final_Fantasy_X%29) You still have Nemesis, though. (http://finalfantasy.wikia.com/wiki/Nemesis_%28Final_Fantasy_X%29)