Ulcerate

The price is the catch. A single black mana for -3/-3 at instant speed is one of the cheapest hard answers black has ever had to a small or midsized creature, but the spell bills you for the rest in life: three points off your total when it resolves. That self-inflicted cost is the whole balancing mechanism, and it puts the card in a particular corner of black's removal suite. Compare the spells that price their efficiency differently: Disfigure shares the one-mana cost but settles for a smaller -2/-2 swing with no life paid, while Tragic Slip wants a creature to die first before it scales up. Ulcerate takes the opposite trade, buying the bigger shrink up front and charging your life total for it. The -3/-3 framing does its own work here too: it lowers toughness rather than dealing damage or destroying, so it slips past indestructible, ignores damage prevention, and answers a threat without ever putting "destroy" on the stack. It also means a toughness buff in response does not save you from the bill: the spell still resolves, the creature just survives, and you still bleed the three. The only way out is the target becoming illegal outright (leaving the battlefield, gaining hexproof), in which case the spell fizzles and no life is lost. All of this makes it a tool for decks that treat their life total as a resource to spend rather than a cushion to protect, which is why the card reads as expensive only to the decks that cannot afford to bleed.