Whirlwind20

If your opponent has any Benched Pokemon, he or she chooses 1 of them and switches it with the Defending Pokemon. (Do the damage before switching the Pokemon.)

Mega Drain40

Remove a number of damage counters from Butterfree equal to half the damage done to the Defending Pokemon (after applying Weakness and Resistance) (rounded up to the nearest 10). If Butterfree has fewer damage counters than that, remove all of them.