Tonberry

A stun counter is the entry tax here, and it is a clever one: the creature comes down tapped, and because a stun counter is consumed during the untap step instead of letting the creature untap, it sits inert for a full cycle and cannot attack until you have paid off that delay. What the wait buys is Chef's Knife. First strike and deathtouch together, but only during your turn, makes this a one-drop that destroys anything foolish enough to block it and walks away unscathed, because first strike lands the deathtouch hit before the blocker can trade back. The color of that pairing is the tell. Black hands out deathtouch freely; bolting it to first strike is usually reserved for costlier bodies or doled out as a temporary buff, since the two combine so lopsidedly in combat. Confining the window to your own turn is the lever that lets it live at one mana: on the opponent's turn it is a plain 2/1 that blocks and trades down like anything else, so the deathtouch reach only surfaces when it is the one pressing the attack. Entering stunned and the my-turn-only clause work the same problem from two directions, keeping a combat profile that would be oppressive at will honest by making it slow to come online and one-sided once it does.