OKay, well then, I guess I'll explain the KH challenge...again. If you follow these steps, it'll bring KH to the max difficulty.
1. Choose Expert mode
2. When you are given the choice of weapons, pick the sword, and give up the shield.
3. When they (tidus, selphie, and wakka) ask you the questions, pick the bottom choices for all. (This will result in you leveling up extra slow for the first 40 level ups)
4. This is the most importants step. Only fight boss battles. In other words, only battles that you must fight (and win) to make the story progress. THat means don't fight any regular heartless unless you must, to click a switch or something for example, and if there's an optional winnable battle, such as Leon or Cloud, let them defeat you. Doing this will keep Sora at the lowest possible level through the game, and it will make it as difficult as it can be to beat the game. Good Luck. Oh, and this step also means that you can't ever participate in the Cup tournaments of the Colliseum, or fight with the islanders on Destiny Islands, etc. No optional fights, run and be a sissy whenever possible, and then it will be the Ultimate Kingdom Heart Challenge.
Oh, and if you'd like to add more challenge, then never equip acceseries, and leave on the Kingdom Key through the whole game. Or you can also try to beat Sephiroth with this amount of power...but as of now...I consider this to be impossible...unless you're extremely skilled, and have at least 2 hours to use on it...
Now, I know that this can be confusing to understand, so if any of you have ANY questions at all, then please ask me. I'll answer them to the best of my abilities.