Luke: I will not fight you, father.
Vader: You are unwise to lower your defenses.
Luke: Your thoughts betray you father. I feel the good in you. The conflict.
Vader: There is no conflict.
Luke: You couldn't bring yourself to kill me before, and I don't believe you'll destroy me now.
Vader: You underestimate the power of the dark side. If you will not fight, then you will meet your destiny.
(favourite part.)