Count Dooku

In the film Attack of the Clones, it is revealed that Count Dooku was once a Jedi who served as an apprentice of Yoda. He was the master of Qui-Gon Jinn, Obi-Wan Kenobi's old teacher.

The film explains that Count Dooku left the Jedi Order after the Battle of Naboo and went to the Dark Side where he adopted the Sith name "Darth Tyranus".

The final big battle scene in Attack of the Clones where the Confederacy of Independent Systems battle the Jedi and clone armies of the Republic has a memorable fight scene between Count Dooku and Yoda. Because Yoda's actions in the fight scene would have been impossible to do with the puppetry used to portray the character in the original trilogy, he was instead animated using Computer Generated Imagery.