Malignus

The clever part of this design is the inversion: it scales off the opponent's life, not yours, so the more comfortably they sit above burn range, the bigger this swings into them. Against a fresh slate it lands as a 10/10 that no fog, no Healing Salve, no damage prevention of any kind can blunt, because the unpreventable clause is built to slam shut exactly the doors a defensive deck would reach for. The mathematics create their own tension: every point of life an opponent gains hands you another half-point of body, which means a lifegain plan does not just fail against this creature, it actively feeds it. The same arithmetic also makes the body brittle in a specific way: because power and toughness recalculate off whatever the opponent's life total currently is, anything that knocks them down (their own painlands, a fetch, a shock from across the table) shrinks Malignus right along with it. Spot removal answers it cleanly, and without haste it sits idle for a turn before swinging, the leash that keeps a potential 10/10 honest at five mana. The reason it earns its slot beyond raw size is how it rewrites the usual race math: the deck across the table cannot stabilize by climbing out of burn range, because climbing is precisely what arms the thing trying to kill them.