Does it have to be a FF character?

If not, it has to be Goofy in KH1. Granted he's a great guy, but in battles he is the worst. He dies all the time no matter what you do and what you set him as. The same goes for Donald, except that he doesn't die as much.

Hopefully both will be much better in KH2 (release date of 22nd Dec for Japan, 22 Feb-ish for NA and Europe I think).