Does Golurk's "Superpower" attack apply Resistance to the +20 damage it does to itself?
Yes, as long as Golurk is Fighting Type at the time of the attack, Resistance would be applied.
Superpower





x2
Bear HugThe Defending Pokémon can't retreat during your opponent's next turn.


SuperpowerYou may do 40 more damage. If you do, this Pokémon does 20 damage to itself.
Does Golurk's "Superpower" attack apply Resistance to the +20 damage it does to itself?
Yes, as long as Golurk is Fighting Type at the time of the attack, Resistance would be applied.