romancing saga 2 - final battle(cheeseed) + ending 

You can beat the final boss without doing this. But I for one was not going back taking out a party member to optimize my party the best it could be.Though if you are bring Crusader,Iris and,Mermaid to this fight. As Iris and Mermaid both negate the main attack that makes your party wipe during the second half of this fight.