Spoilers for KH2 up ahead. :P
I vote for Kairi, since everyone'd probably be killing each other while she is hiding in the bushes, when there is only one person remaining she'd jump out of the bush and call out namine and erase that person's memory and then hit that person's head and then win.
She masters the bush hiding techniques, why else do you think she didn't get pwned by the heartless while running around with sora?
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