To perform it, he steps back and puts his hand forward and charges a purple energy sphere. Then, he fires the energy sphere in the form of a small energy wave at the opponent, inflicting a great amount of damage.
Usage and Power
King Vegeta uses this attack in one of Frieza's flashbacks to execute a Saiyan messenger as punishment for failing to capture planet Tazba on time due to the full moon being three days away.
In Dragon Ball Z: Broly - The Legendary Super Saiyan, King Vegeta is also seen using the Execution Beam on Paragus in the latter's flashback, in response to Paragus's objection to the Saiyan King's planned execution of his son, Broly, before sentencing the Saiyan to be executed alongside his son.