Darth Plagueis The Wise
Anakin on the other hand, was conceived without a father and was supposed to be the chosen one, the one who would bring balance to the force. Now, Darth Plagueis apprentice was Darth Sidious who eventually killed him. I think that Darth Plagueis foresaw his death to Darth Sidious and actually "created" Anakin to avenge his death. In so doing, moving past to Episode VI, it was actually Anakin/Darth Vader who killed Darth Sidious, avenged the death of Darth Plagueis, his creator, and eventually bringing out balance to the Force as prophesized.
My theory: It was said that Darth Plagueis was so powerful that he was able to manipulate the midichlorians and create life itself. « Star Wars: Revenge of the Sith | Main | Going to the Hospital in Bahrain »