Darth Vader

Darth Vader is Emperor Palpatine's right hand Sith of the Galactic Empire. He was once Anakin Skywalker, a proud Jedi knight, but fell to the dark side when he listened to the evil whispers and lies of the Emperor. When fighting off against Obi-Wan Kenobi, another Jedi Knight, Vader succcumbed to the darkness and partially became a Heartless when his limbs were sliced off. Vader was then encased in a black life-support armor that kept him alive as long as he wore the outfit.

When Xehanort arrived on Coruscant, he made a deal with Emperor Palpatine and Vader to join the Horned King's Alliance in exchange for control over the Heartless. Palpatine agreed, and then turned Darth Vader and the Imperial Army into full Heartless. In this new form, the Sith Apprentice was nearly unstoppable and tried to overthrow the Emperor based on his delusions of power. Vader's Heartless met his end at the hands of Sora and his keyblade, and was then reunited with his nobody, who then combined into the original Anakin and destroyed the Emperor by throwing him into the Death Star's core shaft. Anakin then passed away not long afterwards.