@uhu123: Sorry, been busy, but I wish you a merry Christmas anyway.
I am referring to this:
Indicating an amp, whether you interpret it as oneness, the prophecy fulfilling itself or something else entirely.
Him going from weaker than ever (clear hyperbole considering iterations like limbless Mustafar Vader) to gathering all his remaining energy into his last act and then getting some sort of (oneness)-amp upon deciding to turn on the Emperor is not contradictory to each other, and is, in fact, the more likely explanation if one considers consistent power levels, considering ESB Vader was telepathically brought to his knees by a half-serious Sidious from across the galaxy and his equal Luke was stated to be in Sheevs telekinetic one-shot range.
Even without considering Mustafar Vader (and i don't see any reason why we shouldn't include him), that would still include Vader right after he was put into his suit, or when he collapsed a cathedral onto himself and then survived buried alive for days his suit's life support system, something Vader usually depends on to stay alive, yet he endured thanks to the dark side, something he didn't have against Sidious, given that, you know, he was a Jedi at the end of ROTJ:
Either way, he was immensely weaker than his ESB/ROTJ prime as of 19 BBY. It's not hyperbole, it was a literal statement.
Vader was brought down while he was in his shuttle and privately musing about Luke, he wasn't combat ready at all. And for the record, Luke also did something similar shortly after ANH, and that was in the middle of a space battle, a scenario where Vader would no doubt be far more combat ready, yet we all agree he is far above this iteration of Luke:
Thus, that doesn't prove anything in terms of Vader's power relationship with the Emperor. If Vader's mind was "unprotected" during a space battle, I don't see why it wouldn't be while he is in his shuttle musing about Luke.
Not sure why you bring up Martin, who is only an authority on Canon, in a Legends debate, but the "super energy" doesn't come from a random interview, but an officially published source anyway, if you want to go down the "Lucas is a hack who constantly changes his mind"-route.
Martin is an authority in Legends as well, both as a member of the Story Group and especially considering Lucas sold out the franchise in 2012, hence why he deemed SOD as part of Legends as well even though it was primarily created as a Canon comic series:
It changes the fact that Palpatine wouldn't be using his powers to their full extend or directly directed at Vader, which is reflected in the novel:
Also interesting to note that Vaders weakness is only empathized in the minutes leading up to actually killing Sidious, not during the act itself, so the notion of Vader being amped while killing Palpatine is not contradicted.
Except that palpatine not using his full power is never stated in the novel and is indeed directly supported by other sources,a notion that isn't contradicted by later sources:
When the evil Emperor, Supreme Master of the Dark Side of the Force, turned the fullness of his malevolence against Luke, Anakin Skywalker suddenly awoke from the curse that had imprisoned him for so long… Shedding his bleak and soulless identity of Darth Vader, Anakin took the full force of his Dark Master’s evil lightning upon himself - and hurled the Emperor to his death.
-- Dark Empire 1 Endnotes
And the novel itself clearly states the lightning was "tearing into" Vader, so even if the lightning was initially hitting in all directions Vader still took the full brunt of it.
And for the record, the Emperor himself acknowledged Vader as powerful enough to kill him, which wouldn't be the case if Sidious could just one-shot him:
Yes, Vader remained strong in the Force, but strong enough to succeed me? Never. Granted, he was strong enough to kill me. But that only lasted for so long.
-- Jedi vs. Sith: The Essential Guide To The Force
So what if Vader's weakness isn't mentioned again? Aside from the fact that isn't true, omission is not contradiction:
Although it would not have seemed possible, the outpouring of bolts from the Emperor's fingers actually increases in intensity, the sound screaming through the room. Luke's body writhes in pain. Vader grabs the Emperor from behind, fighting for control of the robed figure .
-- Return Of The Jedi Movie Script
As the Emperor continued to strike Luke with his barrage of Sith lightning, Moving awkwardly, he shifted his bulk to stand beside his Master. On the floor, Luke writhed in agony, and was on the verge of death as he groaned, "Father, please. Help me."
Vader watched Luke curl into a fetal position as the Emperor hurled an even more staggering wave of lightning at his victim. Vader had no doubt that Luke was about to die. His son screamed.
Not just my son . . .
The Emperor unleashed another round of lightning.
. . . or Padme's son . . .
Luke screamed louder.
. . . but my son . . . who loves me.
Luke's clothes began to smolder as his body involuntarily spasmed. Suddenly, Vader realized that he was no longer concerned about his own personal future. Despite all the terrible, unspeakable things he'd done in his life, he knew he could not stand by and allow the Emperor to kill Luke. And in that moment of awareness, he was Darth Vader no more.
He was Anakin Skywalker.
, lift him off his feet, and carry him to the open elevator shaft. The wretched Emperor continued to release lightning bolts, but they veered away from Luke and arced back to crash down upon him and his insurgent apprentice. The lightning penetrated Vader's life-support suit and electrified Anakin's organic remains, but he lurched forward until he could throw the Emperor into the elevator shaft.
Palpatine screamed as his body plummeted down the shaft. Still trapped within Darth Vader's armor, Anakin collapsed at the shaft's edge, but heard the explosion of dark energy that consumed the falling Emperor.
-- The Rise And Fall Of Darth Vader
Yet the Emperor still physically struggled against him:
, his hands still shooting bolts of malign energy out in all directions. In his wild flailing, the lightning ripped across the room, tearing into Vader. The Dark Lord fell again, electric currents crackling down his helmet, over his cape, into his heart. Vader stumbled with his load to the middle of the bridge over the black chasm leading to the power core. He held the wailing despot high over his head, and with a final spasm of strength, hurled him into the abyss.
-- Return Of The Jedi
Vader was never stated as more powerful than ever anyway. Sure, that would be understandable if he wasn't so weakened, but he was, thus the best you can argue is that he retrieved most of his power, a notion I myself can agree with.
And there's another key factor to take into account: Vader's death was attributed by sources mostly to his life support system being compromised rather than any weakness relative to the Emperor's power level:
The vast majority of sources portray ROTJ Luke as an equal to his father, without mentioning any circumstances as the reason for it and some outright contradicting this notion.
Yes, they portray Luke as an equal in a scenario where:
1) Luke was enraged for most of the fight, i.e amped:
2) Vader was conflicted, something that was stated by several sources, which would obviously hinder him:
Darth Vader's internal struggles against the faint spark in his soul that was Anakin Skywalker had been thrown into high relief by the Dark Lord's dealings with Luke. The Emperor demanded utter obedience and unquestioning loyalty. Vader vowed to serve his Master, but the words sounded hollow.
-- Star Wars Fact File 55
The Emperor goaded Luke into snatching up his lightsaber, and father and son battled in a rematch of the duel they had fought on Cloud City. During the struggle,Vader's resolve began to flicker as he saw the good in his son.
-- The New Essential Chronology
Set against Luke was his nemesis - The Dark Lord of the Sith. And despite himself, his dark master and the power of the dark side, Darth Vader was beginning to question all that had gone before. Stirring inside was a father's love for his son.
Suddenly the duel was over. Learning that he had a daughter, Vader threatened to turn her if Luke would not join him. Filled with rage, Luke beat down his father, then let go of his anger and weapon.
-- The Official Starships & Vehicles Collection 3
'You'll have to come in and get me,' replied the disembodied voice.
'I will not give you the advantage that easily.' Vader felt his intentions increasingly ambiguous in this conflict; the purity of his evil was being compromised. The boy was clever indeed - Vader knew he must move with extreme caution now.
-- Return Of The Jedi
The fact that this scenario is not mentioned doesn't change its existence. If, say, I were to describe you as an equal to Mike Tyson, but he was weakened or hindered that would obviously change the value of my description entirely, because context is key.