I don't think there is anything in canon stating that Vader was "weaker" in RotJ. Granted, there was underlying conflict/good in him(which both Luke and Palpatine sensed), but I don't know that the "flickering light"(as Palpatine described it) within Vader would have gimped his power or whathaveyou.
Originally posted by Eli Vanto
So you think ROTJ was his peak or??
I will say that said conflict must have been buried pretty deep, as Vader was still willing to bring Luke before Palpatine, then defend Palpatine from Luke's strike, then go on to try and coax Luke towards the dark side -- even Jedi vs. Sith states that Vader was initially trying to turn Luke towards the dark side. It wasn't until Luke was dying right in front of him that Vader finally embraced the underlying good in himself. Prior to that, it didn't seem like Vader was at all prepared to walk away from the dark side/Palpatine.
Maybe the new comic series(which is set between ESB and RotJ) will shed some more light on that aspect of Vader's character.
Vader was indeed conflicted as made clear by Starwars.com and evident from the movie.
Vader and the Emperor waited for Luke to come to them, which he did; the young Jedi believed there was still good in his father, and tried to turn him back to the light side. Vader was conflicted, but still brought Luke before the Dark Lord.
During their duel on the second Death Star, Luke feels the good in Vader and attempts to draw him back from the dark side by lowering his defenses.
This means there were cracks in Vader's surface of dark side emotions through which Luke was able to sense the good in Vader. Compassion for his son was weakening his hatred (eventually overcoming it later in the movie). Even though Vader was still using the dark side to fight, it's possible he couldn't do it in full capacity. How much was this affecting Vader's abilities is hard to quantifie though.
Originally posted by ScizardKind of what I think as well.
But yes I never said he wasn't conflicted, just that I don't think it hinders him unless it gets brought to the surface like when Luke talks to him before they go to meet the Emperor.
Granted the underlying conflict/good was still there, but without Luke in the picture to coax it out of Vader, it don't think it would have been much of a hindrance to his overall abilities.
Make no mistake, Vader was still evil in that era.