That would be the first one I believe. I freaking hated that turquoise-hooded ninja witch looking thing.
Tabuu was easy. It's unlocking Wolf that's hard.
Or Sonic.
Shut the forget up. It never had a stuffty update, you know why? THE LATEST UPDATE DIDN'T DO ANYTHING TO THE loving GAMEPLAY.
Half the fun was shooting someone in the back of the head with a shotgun and watching them fly.