This is the main reason I have stopped playing 8, its too easy.
Better ones for difficulty would be one of the dissidias on hard or most of ff 2 if you stick to the areas you are supposed to go to.
the part in 9 where zidane is in lindblum by himself is a major exploit for that one, in 6 there are several areas where there are weak monsters that give tons of exp and ap, in 4, you level up WAY too quickly and the only problem once you get to the moon is the red dragons, in 1 the whole game is easy, 10 once you get wakka to a certain point he becomes nigh unkillable, twelve, once basch gets a two handed sword its game over for everyone else, especially after you get the bravery skills and stuff, in CC you can level up several times in one fight, and so on. in KH games you just stick to the final dungeon, (except bbs) and so on.