For me I'd have to say the reaction commands when battling Cerberus after you he catches you with his three heads.
My favorite is anti form except if your battling a boss, then your just dreading for it to go away because you can't heal, summon, do anything basicly. It sucks. so mine is either that or master form.
I'm in the middle of critical mode right now and the only problem for me is the HP bar, it's half of what it usually is!
I think it's pronounced Zeeon, well, thats how I pronounce it.
I don't really know on this one, I mean for me Xemnas 2 Data is the hardest but then the first Xemnas is easy so I don't know. I say this 1. Xemnas 2. Axel 3. Zexion
They are probably the next kind of enemy based thing like heartless and nobodies.
Roxas, it gets old after playing as Sora all the time.
FAT BANDITS ARE A PAIN!! I hate them! I basically never go to Agrabah because of them.
My favorite is Follow the Wind because it make cool little skull thing when you hit something and it looks cool.
