Kiku, Night's Flower

The kill condition lives in the math: a creature deals damage to itself equal to its power, so a zero-power blocker or anything already shrunk to zero power by a debuff takes nothing at all, while a fat attacker obligingly punches itself out. The exact wording does real work here. Because the damage equals power, not toughness, the effect only kills when power meets or beats toughness; a 2/4 takes two and walks away. When the damage is lethal it routes through state-based destruction rather than destroying directly, so it does not slip past indestructible, and regeneration still saves the target. The ability targets, too, which means hexproof and shroud shut it off cleanly. That conditional is the price tag bolted onto a repeatable removal engine, and the steep activation plus the 1/1 frame (which invites every burn spell and ping in the game) is the rest of the bill. Compared with the era's flat point-removal, this is a different philosophy: not a spell you cast once and lose, but a permanent that rewards a board where the opponent has committed real power to the table. The assassin lineage has always traded raw efficiency for inevitability, and this is that bargain rendered in pure black: a tap ability that answers, over and over, exactly the oversized creatures that ordinary removal struggles to size up to, provided their power outruns their toughness.