Comeuppance

Deals damage to the last opposing Pokémon to hit the user with a physical or special attack this turn equal to 1.5 times the HP lost by the user from that attack, rounded down. If the user did not lose HP from that attack, this move deals 1 HP of damage instead. If that opposing Pokémon's position is no longer in use and there is another opposing Pokémon on the field, the damage is done to it instead. Only the last hit of a multi-hit attack is counted. Fails if the user was not hit by an opposing Pokémon's physical or special attack this turn.

“The user retaliates with much greater force against the opponent that last inflicted damage on it.”

In-game text, Scarlet & Violet