She-Hulk, Wallbreaker

Combat math normally favors the defender: throw two blockers at an attacker and you either trade profitably or eat one creature to save your life total. This inverts that entirely. Every body committed to stopping a Hero feeds it, one counter per blocker, and those counters stick, so gang-blocking to kill a threat instead builds a bigger one, and chump-blocking a swarm just fattens the whole board over successive turns. Team-wide trample is what closes the loop: the extra size does not stall against the wall of chumps, it punches through them into the defender's life total. What emerges is a payoff that wants a wide Hero board and then punishes the only sane response to a wide board. The 5/5 trampler at the head of it is almost incidental; a single Hero that gets double-blocked and survives comes out larger and harder to profitably answer next combat, and a whole team doing that spirals fast. The clause rewards attacking into blocks rather than around them, which is the opposite instinct most go-wide anthems train, and that reversal is the whole engine.