Anakin Skywalker is the Chosen One. Even though he became Darth Vader he still fulfilled his duty.
Anakin was a slave born on Tatooine. He and his mother were owned by Watto. One day Anakin's life totally changed. He met Qui-Gonn. Together they managed to free Anakin. Anakin's blood contained more midi-chlorians than Master Yoda. Qui-Gon said that Anakin was The Chosen One, the one who would bring balance to the Force. But he was wrong.
In Episode II Anakin reunites with Padme. He takes her to naboo and sparks of romance ignite.
Anakin has nightmares about his mother and rushes to Tatooine. There he meets his stepfather, Cleigg Lars and his stepbrother, Owen. Anakin discovers that his mother was taken by Tuskens. He finds her and she is dying. Shmi dies in Anakin's arms. Anakin gets mad and wipes out the Tusken camp. At the end of the Episode, Padme and Anakin marry.
In Episode III Anakin and his Master rescue Palpatine from the Serperatists. When he geos to Coruscant Padme tells him that she is pregnant. That night Anakin has a nightmare about her dying. He vows to learn how to save her. He asks Palpatine for advice. Anakin discovers he is a Sith Lord. Anakin falls to the dark side and becomes known as Darth Vader.
Vader goes to Mustafar and wipes out the Seperatists. Padme finds him and tells him about the things that Obi Wan told her. vader gets mad and chokes her. Then Obi Wan and Vader duel. Obi Wan wins and Vader is left in a lava pool. His entire body becomes covered in flames.
Hours later, Sidious finds him and takes him to the hospital. There his limbs are replaced with plastoid and he gets put into a black suit that will keep him alive. When Vader wakes up Sidious tells him Padme died. Vader decides to join him fully.