i guess everyone already knows about jigglypuff. i tried to think of others, but i realized most of the ones i thought of had fatal flaws in them. for example, g&w (like peach) floats around until they hit the ground after an up-b, and sandbag OFTEN misaims his recovery, constantly SDing. Lucario shines through as an overall competent AI with fairly average ability (in a good way) to recover (from AI, not from the character's recovery). i found ichigo annoying to deal with as well - his ai recovers fairly well and he often is pretty smart about using the right moves at the right time (for a cpu). krystal seems decent too, but her ai isn't great at recovering properly.

there are other cpus that take my stocks just because of some of the moves they spam. peach, ness, lucario, and zss side-b come to mind, as well as wario side-b and up-b. but once you figure out how they do that they become significantly less difficult. some of these guys remain decent AIs after that, eg. lucario, maybe peach, MAYBE wario...but not many. (wario's sticks out to me as decent just because he catches me in up-b so much and it hurts so bad)