STAR WARS / CLONE WARS

Before Episode3, Anakin fights a duel with Asaji Ventress, who is
Count Dooku's apprentice.[To be accurate, she is not a real sith.Dooku
regards her as a mere soldier. There are always TWO sith, not more or less.
The master is Darth Sidious, and the apprentice is Dooku, so Asaji will not be a sith ,
but "dark jedi"]
In conclusion, Anakin beats her ,but through the duel, he learns how to handle darkside
of the force. In Episode3, at last he changes into Darth Vader, the most powerful sith.
However ,after the duel with Obi-wan ,who WAS his master, he loses a hand and two legs.