I'd argue it's not that difficult. Rather, I think it's just a pain in the ass and beyond tedious. I think, perhaps, one of every item in the game might constitute "perfection" as the OP seeks it. For example, getting 99 of every item which synthesis would take hours upon hours of farming the materials. The mind-numbing monotony would be enough to drive any man to insanity.
That said, I did everything except knocking those bleeding mushrooms around 100 times. It's not particularly difficult as Kingdom Hearts, in general, is not particular difficult. My tolerance for monotonous quests, however, tops out at juggling mushrooms.