Duel on Mustafar

When the couple is reunited, Padmé Amidala pleads with Darth Vader to leave public life with her, but he refuses, believing that he can overthrow Sidious so that he and Padmé can rule the galaxy together. Vader sees Obi-Wan Kenobi emerge from Padmé's ship, and suspects her of betraying him. Enraged, he uses Force Choke to choke Padmé into a coma. 
Obi-Wan and Vader break into a vicious lightsaber duel. The duel brings them out of the facility to unprotected areas of the volcano planet. Obi-Wan eventually gains the advantage of higher ground, and when Vader attempts to attack again, Obi-Wan swiftly dismembers him, removing his legs and non-mechanical arm and leaves him to die. While screaming in agony Vader tumbles down the embankment to the edge of the lava where he catches fire, sustaining near-fatal burns and critical lung damage. Obi-Wan leaves Mustafar with Padmé and Vader's lightsaber, reluctantly leaving Vader to die. Shortly after Vader's defeat, Palpatine rescues Vader and sends his troops to revive his apprentice.
On Coruscant, Vader's missing limbs and damaged body parts are replaced by cybernetic prostheses and implants. Vader is put into a full suit of black armor and is sealed in a respirator mask, which will allow him to survive his injuries. Upon inquiring with Sidious about Padmé's condition, Vader is informed that, in his anger, he himself killed Padmé. Vader unleashes a furious scream of mournful rage and destroys droids and equipment throughout the room with the Force while Sidious looks on with a malicious, contented smile, satisfied that Vader's hatred and rage has survived the mutilation of his body.