Paul Atreides Vs. Darth Vader
Vader after having his ship hit and sent spinning out of control at the end of Ep: IV, is sucked into a 'spacial disturbance' which sends him barreling through time, space and dimensions to come out in Herbert's Dune universe and promptly crash lands on planet Arrakis (Dune) itself.
Having been tracked as an unknown ship by the planets surveillance, Paul's Fremen troops are dispatched to investigate, where a pissed off Vader, not caring for sand in his underwear and the jabbering of a bunch of cocky blue-eyed sand dwellers, quickly dispatches them.
Hearing the death cries of his troops, Paul sets off to face this unknown force in the desert, Lord Vader Vs. freshly appointed Emperor Atreides.
Vader gets his full use of the Force despite it being a different universe and light-saber. Paul gets the use of his powers, he no longer needs the focusing device and his Fremen blade. Who wins? For the sake of argument, worms will not disturb this battle.