~Defeat Penance~

Penance is the most powerful boss in the game and was unique to the International Version of the game. If you're not using Yojimbo it's a very long fight, not difficult but is a very slow fight. Your party should have maximum stats and a high (120+) luck stat to be able to defeat it. To simply fight it you'll need to defeat all the Dark Aeons to get it to appear. Once there you can select to fight it from the Airship destination list. Whether you choose to use Yojimbo or not, once it's dead you'll earn this trophy.