Mockingbird, Bobbi Morse

Growing by taking hits is a green or red instinct: the fight-and-survive loop, the swell-when-damaged body. This is white borrowing it, and the parenthetical carries the whole design. She must survive the damage to earn the counter, so lethal is still lethal and the ability only rewards blows she can walk away from. The sequencing is stricter than it looks, and unforgiving of wishful thinking. When damage is dealt, state-based actions check immediately: if her toughness holds, she stays; if it does not, she is gone before the trigger ever reaches the stack. There is no grace period. So the counter is not a lifeline; it is the reward for a clash she was already going to win, and she banks that size permanently. Block a smaller attacker and she comes back a 4/4. Get poked by a pinger, clipped by a fight spell, or caught in your own damage-based effect, and each nonlethal ping is toughness spent to buy toughness kept, which quietly makes her harder to remove by the same means that just failed. That inversion (a body whose trading upside compounds every turn she endures) is the point, and it feeds anything that cares about +1/+1 counters as a resource, giving a stubborn frame a second reason to stay on the table beyond the flavor of a spy who refuses to stay down.