Gengar MODFO 20

Once during your turn (before your attack), you may move 1 damage counter from 1 of your opponent's Pokémon to another (even if it would Knock Out the other Pokémon). This power can't be used if Gengar is affected by a Special Condition.

If your opponent has any Benched Pokémon, choose 1 of them and this attack does 10 damage to it. (Don't apply Weakness and Resistance for Benched Pokémon.)