Grim Affliction

A removal spell that pays for its own modesty. A single -1/-1 counter on the target rarely closes the deal by itself, but the proliferate clause attached to it is where the spell stops being a -1/-1 shrink and becomes a board-wide tool. The same proliferate that adds a second -1/-1 counter to the creature it just hit can also stack damage on every other -1/-1 counter already in play, advance loyalty on planeswalkers, tick up a poison count, or push along whatever charge counters happen to be sitting around. That dual purpose is the design logic: the spell is built to reward a board state that already has counters on it, so the more the game has been going your way (or the more your deck is built to spread -1/-1 counters), the more this instant does on resolution. Played into an empty board it is a slow, expensive shrink ray; played into a developed counter-matters position it removes one creature while quietly finishing several others. The instant-speed timing carries more weight than the rate suggests: holding it up lets the proliferate respond to a board that just grew, picking up counters that were not there when the turn began. It is a piece of black removal whose ceiling is set entirely by the deck around it, the proliferate doing structural work that a straight kill spell never offers.