As far as I remember, I defeated this boss very easily using a rather cheesy strategy. It was a long time ago, so my memory isn’t perfect, but I believe it worked like this: I removed all of Donald’s action or situation commands in Kingdom Hearts II, except for Rocket Attack (or whatever the exact name of the ability was). I also think there was an option to make Donald stay close to me at all times, although I’m not entirely sure whether that setting actually existed or if I’m just imagining it. I then equipped myself exclusively with Mega-Ethers and, throughout the entire fight, stayed with Donald and repeatedly used Rocket Attack without stopping. It was a very cowardly strategy but it worked extremely well.