Quote? Because all it says is that he had the potential to be "one of the most powerful Jedi of all time," or something to that effect. No mention of Anakin's baseline being stunted, and there are various sources that already say Anakin was already the most powerful Jedi of all time. Etc.
The quote apparently changed since I last saw it, or the original was removed, or I misremembered. The gist stays the same, Vader is weaker than Anakin.
On the Star Wars Database link provided by Mythlord, the picture with Sidious looking at Vader on the table states:
"Sidious knew that Vader's broken body would make him weaker than before, but tested his apprentice's connection to the dark side by telling him that he had caused Padme's death. The intensity of Vader's anguish and self-hatred made it clear that he still possessed great power."
So basically saying Sidious was sure Vader would be weaker, he tested Vader's connection to the Dark Side, and went "Well, I was wrong."
With that said, Luke was definitely conflicted while fighting Vader, as was made clear throughout the entirety of Return of the Jedi. He constantly stated that he didn't want to fight Vader. Repeatedly. Like a broken record.
When he told Ben that he couldn't kill his own father, Ben told him "then the Emperor has already won," implying that Ben intended for Luke to kill Vader. Yoda supposedly intended the same thing. Ben and Yoda both tried their hardest to stop Luke from confronting Vader in ESB, and yet in RotJ, they insist that he has to confront Vader, that the only thing left for Luke to do was confront Vader. Yoda and Vader both imply that Luke has grown between ESB and RotJ, with both of them commenting on Luke's training being essentially complete, and with both Vader and Sidious commenting on how powerful Luke has become.
Everything in RotJ points to Luke having surpassed Vader. Yoda and Ben both telling Luke to confront Vader, after they had previously warned him that he was not ready in ESB. Sidious and Vader commenting on how powerful Luke is, with Vader specifically saying "Indeed you are powerful, as the Emperor has foreseen," with the Emperor being the character who foresaw Luke being powerful enough to destroy both himself and Vader. Luke holding the upper hand for the entirety of the fight when he's actually trying (He's only put on the defensive after he willingly surrendered and claimed he wouldn't fight any more). Sidious insisting that Luke kill Vader, his most powerful asset at the time, which he would have no reason to do unless Luke had truly surpassed Vader. Two canon sources, Return of the Jedi: Beware the Power of the Dark Side Backstories: Star Wars: Darth Vader - Sith Lord. And the utter lack of canon evidence that Vader was more powerful than Luke.
Even if we look to Legends, Shadows of the Empire has Vader speculating that Luke is already as powerful as Anakin had been in Empire Strikes Back. The Return of the Jedi novelization implies that Luke has surpassed his father, and repeatedly tells us that Sidious was afraid of how powerful Luke was. When Luke tells Vader that Vader will be forced to kill him when the met on Endor, the novelization has Vader thinking "This was not his wish, but the boy was strong--if it came at last to blows, yes, he would destroy Luke. He could not afford to hold back, as he once had." So clearly the novel has Vader seeing Luke as, at the very least, a near-equal. Someone he can't defeat without going all-out. During the actual duel, we get this line from Vader's thoughts, "For the first time, the thought entered Vader's consciousness that his son might best him. He was astounded by the strength Luke had acquired since their last duel, in the Cloud City--not to mention the boy's timing, which had been honed to a thought's-breadth. This was an unexpected circumstance. Unexpected and unwelcome. Vader felt humiliation crawling in on the tail of his first reaction, which was surprise, and his second, which was fear. And then the edge of the humiliation curled up, to reveal bald anger. And now he wanted revenge." On top of that, we have the original Marvel adaptation stating that Luke had grown in the interim between ESB and RotJ, and that if there was any advantage to be had in their duel, it was on Luke's side.
The biggest piece of evidence Legends provides for RotJ Luke being less powerful than Vader was Luke's speculation in The Courtship of Princess Leia. And at the time, Luke had a brain hemorrhage and was not thinking coherently, and was also an unreliable narrator throughout that book (Believing Gethzerion was only a Vader-level foe, when Palpatine was so afraid of her that he invested a great deal of resources to ensure she could never leave Dathomir, rather than just sending Vader to kill her like he sent Grievous to kill Talzin).
The quote basically says Palpatine 'knew' Vader would be weaker now that he lost his limbs. He had Vader rebuilt, but was expecting something weak. Instead, when he tested Vader, he found that Vader "still possessed great power." In other words, he expected garbage, and instead found that his apprentice was still powerful. Coupled with other canon sources like the 2015 Darth Vader comic, 2017 Darth Vader comic, and Lords of the Sith, canon provides tons of examples of Vader being stronger than Anakin, not weaker.
Darth Vader 2015: Sidious tells Vader "You are everything I could have hoped for" in the final chapter. Vader also sees himself as more powerful than Anakin in one of the last chapters of the series.
Darth Vader 2017: Vader briefly man-handled Sidious with the Force, and is allowed to do all the work he wants on his suit, meaning canon Vader doesn't have the same limitations in the suit that Legends Vader had (the suit being intentionally ill-fitting, the limbs not responding properly, ect.)
Lords of the Sith: On literally the first page of chapter one, "His injuries had deformed his body, left it broken, but they'd perfected his spirit, strengthened his connection to the Force. Suffering had birthed insight." Page two says: "When man and machine were one, he no longer felt the absence of his legs or arms, the pain of his flesh, but the hate remained, and the rage still burned. Those, he never relinquished, and he never felt more connected to the Force than when his fury burned." "The armor separated him from the galaxy, from everyone, made him singular, freed him from the needs of the flesh, the concerns of the body that once had plagued him, and allowed him to focus solely on his relationship to the Force."
Last edited by Underachiever59 on Oct 22nd, 2017 at 10:01 PM
Precisely, he knew. Not thought or believed; knew. The fact that Vader still possessed great power doesn't change the fact that he was weaker without his limbs.
Only Luke is specifically Legends, unless Son of Dathomir is a Legends product. Hint: it isn't.
That's also not what the quote says. And given that Sidious continuously tries to replace Vader, and is continuously proven wrong, Palpatine obviously doesn't know shit.
Which could mean a variety of things, least of which is apparently power in the Force. Either way, what Sidious "knows" does not make it a fact, regardless of how logical you feel that should be.
No, the fact that Palpatine thinks he has a numerous ways of replacing Vader and constantly fails means that Palpatine does not know exactly how powerful Vader is relatively. Which is the only thing relevant to this thread. The fact that he has to test Vader at all shows this.