Darth Vader (OP)

"A young Jedi named Darth Vader, who was a pupil of mine until he turned to evil, helped the Empire hunt down and destroy the Jedi Knights...He betrayed and murdered your father."

- Obi-Wan Kenobi to Luke Skywalker.

Darth Vader, born Vader, was a Jedi Knight during the Clone Wars who fell to the dark side. A former Padawan of Jedi Master Obi-Wan Kenobi and a friend of Anakin Skywalker, Vader apprenticed to Darth Sidious and had a hand in the destruction of the Galactic Republic and the rise of the Galactic Empire. He served as the right hand man to Sidious.

After being anointed Darth Vader, the young Sith Lord led the 501st Legion in an assault on the Jedi Temple. There, he confronted his friend Anakin Skywalker. Though Skywalker's strength was formidable, Vader struck him down.

Vader was confronted by Kenobi after the Sith Lord slaughtered the Separatist Council on Mustafar. They two engaged in a duel that left Kenobi victorious and Vader crippled, maimed and burned. Vader was recovered by Sidious. Darth Vader's injuries and fourth-degree burns to the bone required him to wear a life-support suit for the rest of his life.

What Vader and Sidious didn't know was that Skywalker had married Senator Padme Amidala in secret and Amidala had recently given birth to twins, Luke and Leia. Kenobi and Jedi Grand Master Yoda took them into hiding.

Vader attempted to defend the Death Star during the Battle of Yavin in his Advanced TIE Fighter. During the battle, he came across Luke Skywalker, whom Vader sensed the Force was strong in. For Vader could kill another Skywalker, his fighter escort was shot up by Han Solo in the Millennium Falcon.

After the battle, Vader made it his personal mission to identify the identity of the pilot who destroyed the Death Star. His spies and a bounty hunter reported that his surname was "Skywalker". Vader, determined to rule the galaxy, planned to persuade the young Jedi to become his apprentice and overthrow Sidious.

Behind the scene notes
This is based on Darth Vader and Anakin Skywalker being two separate individuals until the writing of Empire Strikes Back. "So what I told you was true, when I told it to you.