Oathsworn Knight

The four +1/+1 counters here are not a growth engine; they are a stack of lives spent one at a time. A 0/0 that arrives as a 4/4 which cannot take damage until its counters run out is really a creature with four lives, and the prevention wording means the size of the hit is irrelevant: a single ping and a lethal alpha strike both cost it exactly one counter. A normal creature dies to one sufficient hit; this one shrinks by exactly one every time it takes any damage at all, so a chump block, a one-damage burn spell, and a giant trampling swing are all equally efficient at grinding it down. What balances that resilience is the compulsory attack. Left alone, this would be an infuriating body that never dies to combat and never has to commit; forcing it to swing each turn hands the opponent the initiative, letting them shave counters through blocks until the fourth one comes off and the creature dies as a 0/0 to state-based actions. Crucially, the prevention only touches damage. Destruction and -X/-X sail right past the counters, which is why the more common answers (a kill spell, a shrink effect) ignore the resilience entirely and only combat and burn have to chew through it. The tension between a stubborn front end and an inevitable decline, escorted along by its own forced aggression, is the point.