Vanquish

The whole spell hinges on a word: blocking. You cannot point it at a creature standing idle, only at one already committed to the combat math, which collapses its window to the span of combat. That restriction is what cheapens it: a three-mana instant that destroys any creature unconditionally would be priced higher, but tying the kill to a creature already blocking turns it into a punishment rather than an answer. The aggressor sets the trap by attacking; the blocker walks into it, and the spell removes the wall without trading a body. It is removal that only the player on the offensive can profitably use, which is an unusual axis for white, a color that more often sits behind its own blockers. The catch runs the other way too: against a defensive opponent who simply refuses to block, the card does nothing, sitting dead in hand until combat goes the way you want. That conditionality is why this style of removal never crowded out the unconditional white answers that came before and after it. It is a precise tool for a precise situation: you are attacking, they block to survive, and you would rather pay three mana than lose your attacker in the exchange.