Mawile (GE #24)

Choose 1 face-down Prize card (yours or your opponent's) and put it face up. If that card is a Supporter card, use the effect of that card as the effect of this attack. (That card remains face up for the rest of the game.)

During your next turn, if an attack does damage to the Defending Pokémon (after applying Weakness and Resistance), that attack does 20 more damage.