Vader vs. Cyborg Anakin
Darth Vader (as of ROTJ) vs. Cyborg Anakin.
For purposes of this fight, assume Cyborg Anakin somehow survived Death Star II, got a new mechanical hand, and a new lightsaber to go with it.
Essentially, is Vader's conflicted Dark Side use stronger then the at last unconflicted use of the light Anakin just regained access to.