CT1138, it gets even muddier than that when you factor in stuff written for the OT and prior two PT films -- but also either cut or forgotten/retconned by George. In the original take, back when Anakin and Vader were separate and there was no stigma to a Jedi having a family, Ben and Annikin [sic] were some of the only Jedi still out there toward the end of the Purge. I think in his notes George said Anakin
was the last taken out by Vader -- that Anakin lay dying or dead while Ben fought Vader on the edge of a "molten pit" (George's notes imply both lava and a nuclear reactor, variously). And there was some stuff about Anakin not actually dying, but limping along for a while with extensive cybernetics. A lot of that made it into The Star Wars (Dark Horse's adaptation of George's original story). Vader originally was battle-scarred, yes, but only wore the mask for the crossing in vacuum to board the Princess' ship. I feel like the decision to keep Vader's mask on for the whole film to keep him more menacing started things percolating in the back of George's mind, that didn't fully coalesce until the story sessions for ESB when they were trying to figure out what devastating thing Vader could say to shatter Luke's world. After that, all the cybernetics that had been Anakin's final days got fused with Vader, and the duel by the molten pit was a good source for that damage. Some of the cut dialogue from ROTJ elaborated on what we were shown in ROTS:
BEN: “When I saw what has become of him, I tried to dissuade him, to draw him back from the dark side. We fought … your father fell into a molten pit. When your father clawed his way out of that fiery pool, the change had been burned into him forever–he was Darth Vader., without a trace of Anakin Skywalker. Irredeemably dark. Scarred. Kept alive only by machinery and his own black will …”
Then there was stuff in AOTC and ROTS that played with that portion of George's backstory. And I don't know why he kept cutting it. In AOTC, after getting back from his failed rescue of his mother, and tells Padme he killed all the Sandpeople, a lot got trimmed from the final version (although some of it is in the digital release):
ANAKIN: "I... I killed them. I killed them all. They're dead, every single one of them... Not just the men, but the women and the children
too. They're like animals, and I slaughtered them like animals... I hate them! Why do I hate them? I didn't... I couldn't... I couldn't control myself. I... I don't want to hate them... But I just can't forgive them."
PADMÉ: "To be angry is to be human."
ANAKIN: "To control your anger is to be a Jedi."
PADMÉ: "Ssshhh... you're human."
ANAKIN: "No, I'm a Jedi. I know I'm better than this. I'm sorry, I'm so sorry!"
PADMÉ: "You're like everyone else..."
He keeps cutting all the compelling stuff. I's almost like George is allergic to nuance...