Raging Gorilla

The pump effect lives on the body rather than in a separate spell, and combat math fires the trigger the moment the creature blocks or becomes blocked. The mandatory +2/-2 turns a 2/3 into a 4/1, killing most early creatures it trades with while clinging to a single point of toughness. The result is a permanent that carries combat value forward across turns instead of burning a card slot for one swing, paid for by the toughness it sheds in any combat it enters. That payment is also the leash: a creature that simply got +2/+0 on every block would dominate, but the shrinking toughness keeps the rate from running away by making each engagement a calculated risk. It reads scariest as an attacker. Let it through and you eat a clean 2; block it and you face a 4/1 returning fire that can split open whatever stood in its way. On defense it is far more fragile, because being forced to block a threat it cannot finish leaves a 4/1 that takes lethal damage the same step from anything dealing it one or more, the chip the -2 already started. As an early attempt at folding a pump effect into a permanent, it captures the central tension cleanly: the same swing that makes the Gorilla a threat is the one that leaves it one good blow from dying, every turn it chooses to fight.