Necrotic Wound

Removal that scales with your own graveyard puts a tension into the card that most kill spells avoid: the -X/-X line is worthless when you have no dead creatures and lethal to almost anything by the midgame, so the card asks a self-mill or attrition deck to fuel it before it can cash in. The clever part is the exile rider, and it is broader than it first reads: if the targeted creature would die at any point this turn, from your shrink, from combat, from a second removal spell, from a sacrifice, it is exiled instead. That folds two questions into one mana. It is not unconditional exile (a creature whose toughness outstrips your graveyard count survives, still shrunk but alive), but anything that does die while the effect hangs around dies permanently, which neuters death triggers, regeneration, and graveyard recursion in a single instant-speed window. And because -X/-X shrinks toughness rather than dealing damage or destroying, it kills indestructible creatures outright, then exiles them for good measure. The undergrowth keyword is doing the real structural work: it turns the creatures you have already lost into a resource, so a board you traded away early becomes the engine that answers the threat closing out the late game. That makes it a removal spell whose ceiling rises exactly as the games it is meant to win get longer, and one that punishes the very recursion strategies it competes against.