I'd say Star Ocean 4. Getting all trophies with a guide is absolute hell. Getting them without a guide is probably one of the most ridiculous and sadistic things in the history of entertainment, because:
-You have to open all chests in the game.
-Create all items in the item creation thingy.
-Collect 100% of all data (monster, ship etc).
-Unlock all members' endings (which means you will have to talk to everyone at specific points to progress their meter).
-Play with all characters to unlock their in-game battle trophies (there is a lot of them).
-Complete everything related to side quests.
-Kill the super bosses.
-Beat the game three times.
The two hardest difficulties are unlocked after beating the game and endgame on the hardest difficulty can be quite brutal. Oh yeah, a lot of the above is missable, so you probably need at least three playthroughs anyway. Do not do this without a guide. Even with a guide, you can probably get 20-30 other platinums during the same time it takes to get this one.