Enrage

An X-spell pump effect that scales with your mana but only ever moves power, never toughness, which tells you exactly what it was built for: pushing damage through, not surviving a block. Pour mana into a creature and you can punch for lethal in one combat step or finish off a player who tapped out, but the target stays just as fragile as it started, so it folds to any removal or chump in response and the mana evaporates with it. That gamble is the entire point. The instant speed is the redeeming feature, since a pump trick that only shifted power would be telegraphed as a sorcery; here you can hold up the mana and decide after attacks are declared whether the math reaches lethal. It sits with red's other "spend everything on one swing" effects (Brute Force and the general all-in-on-damage school), but the +X/+0 line keeps it a finisher rather than a tool for winning races: it can push through enough damage to kill a blocker, but adds no toughness to survive one. A closer disguised as a combat trick, and a reminder that in red, toughness was always the resource the color was never allowed to buy.