Eternal Isolation

The power-4-or-greater clause is the whole balancing mechanism: it locks this answer to the fatties white is supposed to fear (the dragons, the demons, the reanimated titans) while leaving small aggressive creatures untouched. Where white's premier removal, the Swords to Plowshares and Path to Exile lineage, buys unconditional reach at the cost of handing the opponent life or a land, this trades in the opposite direction. It answers only the top of the curve, but does so at a clean two mana with no downside to concede. Bottoming rather than destroying is the tell: the threat leaves the board and cannot be recurred from a graveyard, but it is not exiled, and a deck that can shuffle its own library and dig aggressively can eventually see it again. So the answer is hard against a slow deck sitting on its assembled bomb and softer against one built to churn through its deck: the same spell, two very different clocks depending on who cast the creature. The condition is what gives it precision. Not just any creature, and not merely an attacker, but specifically the big thing the opponent spent the game building toward. That precision is also the liability. Facing a swarm of two-power tokens, it has nothing legal to point at and rots in hand, useful only against the exact class of card it was designed to punish. Narrow answers live and die by whether the threat they answer shows up.