Photon Blast is a variation of the Photon Wave used by Dr. Gero in video games.
Overview
Android 20 holds out his hands and fires a purple energy sphere at the opponent, inflicting massive damage.
Video Game Appearances
The attack is called Energy Discharge Blast in Dragon Ball Z: Super Butōden. It was named Photon Blast in Dragon Ball Z: Supersonic Warriors 2, where it appears as one of Dr. Gero's super attacks.