Lockjaw Snapper

Most wither creatures are content to deal their -1/-1 counters in combat and leave it there; this Scarecrow turns the board's accumulated shrinkage into one last detonation when it dies. The trigger is indiscriminate about provenance: any creature already wearing a -1/-1 counter, whether from this thing's own wither damage, an opponent's effect, or some unrelated exchange across the table, takes one more. That makes both ways of interacting with it a tax. Block it, and anything that survives the wither damage now carries the counter its death will finish off. Kill it in combat or with damage-based removal, and the death trigger collects on every weakened creature at once. The permanence of -1/-1 counters is the entire engine: combat damage washes off and is forgotten, but a -1/-1 counter stays, so the snapper spends every turn quietly assembling a kill list and cashing it the moment it dies, scaling its payoff to how much attrition the table has already absorbed. The one seam in the design is the trigger's reliance on death specifically: exile and bounce slip past it entirely, leaving the assembled counters stranded with nothing to fire them. Against damage and sacrifice it behaves as a delayed sweep whose size the other side sets by attacking, blocking, or simply waiting. It rewards counter-based attrition that is already underway rather than asking you to build that engine from scratch, and the 2/2 body is the bait that hides how much board it can take down on the way out.