Count Dooku

"It is obvious this contest cannot be decided by our knowledge of the Force...but by our skills with a lightsaber."

- ~Count Dooku

In Star Wars Episodes II and II, Count Dooku (played by Christopher Lee), also known as Darth Tyranus, is a Sith Lord and commander of the Trade Federation. He and his master, Darth Sidious, give orders to officers and commanders of the Trade Federation, including General Greivous. Dooku also holds a Sith apprentice of his own, named Asajj Ventress. Dooku is a challenging opponent in lightsaber wielding, and usually has the upper hand due to his interesting fighting techniques and many years of experience. However, he was killed in Star Wars Episode III: Revenge of the Sith by Anakin Skywalker, the apprentice of Obi-Wan Kenobi.

Count Dooku tends to flee from battle to save himself, but he is not as nearly as cowardly as Greivous. Dooku was once a Jedi himself, and he had a Jedi apprentice, Qui-Gon Jinn. Qui-Gon was the master of Obi-Wan Kenobi. Once Dooku turned to the dark side, he could not turn back and quickly gained power both in authority and knowledge of the dark side of the Force.

Former Jedi Apprentice
As mentioned earlier, Qui-Gon Jinn's master was Count Dooku. After Dooku turned to the dark side, Qui-Gon took his own apprentice, Obi-Wan Kenobi.

Master Sifo-Dyas
Jedi Master Sifo-Dyas was a leading member of the Jedi Council before he died ten years before Obi-Wan's arrival on Kamino. Sifo-Dyas was once a friend of Dooku. As part of Dooku's test and transformation to the dark side, he killed Sifo-Dyas and took his lightsaber, which he gave to General Greivous, who was yet to become a dangerous Separatist leader and Jedi hunter. Dooku also used Sifo-Dyas's dead body as a blood transfusion for Greivous.

Videos
This video clip is taken from Star Wars Episode II: Attack of the Clones, where Obi-Wan, Anakin, and Yoda step up and face Count Dooku, at separate times. BvnwLLXHabg&fmt=18

In this video Anakin and Obi-Wan work together and face Count Dooku, and Anakin kills him. This is from Star Wars Episode III: Revenge of the Sith. HLlf5bC1wxg&fmt=22