If, on the previous turn, the user's last move missed, failed to affect each of its targets, or was prevented from being used due to an effect such as paralysis, Stomping Tantrum's power is doubled from 75 to 150.
If the user was recharging, grabbed by Sky Drop, or any target of the user's last move blocked it with a protection move such as Protect on the previous turn, Stomping Tantrum's base power is not doubled.
Stomping Tantrum (Bulbapedia)
