Darth Vader: I’ve been waiting for you, Obi-Wan. We meet again at last. The circle is now complete. When I left you, I was but the learner. Now I am the master.

Ben Kenobi: Only a master of evil, Darth.

Darth Vader: Your powers are weak, old man.

Ben Kenobi: You can’t win, Darth. If you strike me down… I shall become more powerful than you can possibly imagine.

From the movie Star Wars: Episode IV – A New Hope (1977)