If my opponent has no benched Pokemon, do I do 30 damage to their active Pokemon when I use Mawile's "Invite and Strike" attack?
No, damage is only done to the "new Active Pokemon". If there is no switch, then no damage is done.
Invite and Strike



×2
-30
Invite and StrikeSwitch in 1 of your opponent's Benched Pokémon to the Active Spot. This attack does 30 damage to the new Active Pokémon.


Sharp FangIt uses its docile-looking face to lull foes into complacency, then bites with its huge, relentless jaws.
If my opponent has no benched Pokemon, do I do 30 damage to their active Pokemon when I use Mawile's "Invite and Strike" attack?
No, damage is only done to the "new Active Pokemon". If there is no switch, then no damage is done.