Umm.. I think it is mathematically impossible to beat tank. Suposing he does the minimum damage always (10), and you invest in attack (~20), he takes you out in 9 turns, which means you have to deal a total of 700 damage in less than 10 rounds -> 78 per round.
For these who are struggling to win the tournament, I advise you to go to the PRACTICE mode. Choose a player, know its special moves and practice the timing. This is all. PS: oh, the music.. aaah yes! I think I'll leave the game open ^^