Darth Vader was first in this episode. Anakin betrayed the Jedi Order. He killed multiple Jedi in Order 66. He worked for Lord Sidious. Through the Dark Side, he even lost his wife Padame, his two children, and his friend Obi-Wan Kenobi.
Darth Vader was seen with his robotic suit with a huge role. He captures Princess Leia and destroys the planet of Aldaraan. He is seen protecting the Death Star in the end of the Episode. He kills Obi-Wan Kenobi at the Death Star.
Darth Vader had a lesser role. While he appeared, the story was more focused on Luke Skywalker.
Vader manages to capture Luke and brings him to Sidious. Refusing to join the dark side of the force, Darth and Luke face-off. As Luke beats him yet still refuses the dark side, Sidious continues to shock him. Vader then carries Sidious and throws him into a pit. Vader dies moments later from his wounds.
Revenge of the SithEdit
In Revenge of the Sith, the player can play as Anakin Skywalker. The player will also have to fight him in the final mission.
In Star Wars Battlefront, Darth Vader is a playable character in multiple missions in both games. He can be played through a bonus in Battlefront 2.