Polliwallop

A fight spell asks your creature to trade blows and hope it survives; this one refuses the exchange entirely. Damage flows in one direction only, at twice your creature's power, so your attacker never takes a scratch. That turns any midsized attacker into a removal spell with no return fire: a four-power creature erases an eight-toughness threat and walks away untouched, with no combat step for the opponent to trick their way through. The affinity clause is what changes the deck it lives in. Priced against a Frog board, the discount scales with commitment: the more Frogs already on the table, the closer this drifts toward a one-mana instant that swings a beating the opponent cannot answer. Affinity for a creature type rather than artifacts is the wrinkle worth dwelling on, because it grafts a cost-reduction mechanic long associated with fast, breakable artifact decks onto something as grounded as a tribal ground-pounder. The reduction rewards the same wide, cheap board a Frog aggro deck wants to build anyway, so the spell asks nothing extra of the builder: play the creatures you were already playing, and the removal gets cheaper as a byproduct. It reads as tribal support that happens to double as instant-speed interaction, doing a fight spell's job without the mutual-destruction clause that usually keeps those honest.