From the Super Mario Wiki
The Piledriver is a powerful move that Wario could perform in Wario World. By picking up an enemy, the player could then jump and press . Wario would spin in the air and pound the enemy headfirst into the ground, almost always defeating it.
In addition, the Piledriver sends out a shock wave that can damage or defeat any nearby enemies. It is similar to the Ground Pound, which Wario can also do.