The final (well technically it's the penultimate) boss fight, against Rival. You'll notice that one of her transformations is Lenneth Valkyrie, from Valkyrie Profile. I hadn't played the game for at least a year when I made this video so I'm a little rusty. However, I did deliberately let "Lenneth" beat me to a pulp so that she would perform her Nibelung Valesti.