Xero in Kingdom Hearts: Reloaded and defeated by Houka in the boy's attempts to locate and destroy the universal threat of Xero in attempt to stop the Heartless swarms within the universe. Alpha is part of a group known as the Trinity Heartless, a group of very powerful Heartless, said to be some of the strongest Heartless that ever existed created by Xero naturally. Alpha is the strongest of the Heartless Trinity.
Kingdom Hearts Reloaded
Right after the events of Kingdom Hearts II the being Xero was created from immense darkness, from that darkness Xero birthed three strong Heartless servants known as Alpha, Omega , and Delta. Using the powers of his Heartless Trinity as he called him joined with his, Xero made the Heartless swarm through the worlds. Alpha and the rest of the Heartless Trinity are main core power sources for the Heartless Swarm and after their destruction and the destruction of Xero, the Heartless reduce back to their normal amounts.
Dark Element: A creation from the darkness itself, Alpha has the ability to manipulate the elements of darkness form within.
Annihalation: Most of Alpha's powers and abilites relate to annihalation and most of his powers are rather destructive in nature, a known ability of Alpha is that he can create a monstorous blast of energy which has been known to wipe out entire areas.
Kingdom Hearts: Reloaded
Alpha appears numerous times throughout the game in many cutscenes, conversing with Delta and Omega or taking orders from Xero himself. Alpha doesn't make an actual in-game appearance till towards the end of the game when he has his battle with Houka...in which Alpha ultimately is destroyed.