I loved fighting Demyx. Yes that time crap was killing me. I died about fifty times before I actually killed him. He moved too freaked much. And his moves very very fast. I couldn't attack him as he used that water wall thingy. I turned to that anti-Sora thingy about twelve times. That's why I died so many times.
Same here. The time limit thing was really annoying (where's the logic of it, anyway?) and I went into Anti form dozens of times. Probably because I had used Valor form atleast 3 times just before I fought him - must have added to the hidden calculator that counts the probability of going into Anti-Form.
Second hardest was definitely Xaldin. I actually died on purpose so I could get Mickey to help. Not that he was much use. But atleast I managed to beat him on the third try. It took me atleast 10 tries to kill off Demyx.