Mm, I don't know how impressive this is, but it was by far the hardest thing I've ever done in KH: Final Mix.
I beat Sephiroth at level 81 on Proud Mode.
I started trying to fight him around level 60-something, but the fact that I didn't have MP Rage made it ridiculously difficult. In fact, I still didn't have MP Rage when I beat him 20 levels later. Needless to say, I got pretty darn good at conserving MP. ^^;
Hmm...what else have I done? Oh. I beat Riku II with the Fairy Harp and the Divine Rose. I used the Fairy Harp on my first playthrough, when I didn't know I could go get the Metal Chocobo and Olympia Keychains from the Hercules Cup. ^^; It took me close to twenty tries (and twenty views of that agonizingly long cutscene before the fight), but I eventually did it.
The Divine Rose thing was an accident. You're not supposed to be able to get it until the second trip to Hollow Bastion, but I fell off of some platform and had to go all the way back to the Entrance Hall. I mistakenly stumbled into the Library, and BAM: Beast/Belle reunion scene. Beating Riku II with that Keychain equipped was sooo easy. :3
