Vader was the most powerful being in the force, or so it would've been if he hadn't been killed by Obi Wan's plot armor. But if Anakin had actually won the duel, how would the OT have turned out? How long would Vader have learned from Palpatine until inevitably killing him and turning into the final Dark lord of the Sith? Would Luke have been able to stop his father if he had fully immersed himself in the darkside under the Emperor's tutelage? Would there really have been anyone that could stop him?
Where were you in '77?