I guess I should get this out of the way now - I'm a huge Star Wars fan. My first living memory is watching the original Star Wars (now known as A New Hope). While I didn't loathe the new (old) trilogy as much as most people, I still found it to be an abject disappointment.
The biggest issue I had was the treatment of Yoda. Sure, that he be a crazy flipping lightsaber wielding maniac was acceptable - something was needed to attract the kiddies - but my greatest issue with the whole thing was that he fought Palpatine, saw every trick in the book, and when it came time to train Luke, DIDN'T BOTHER TO TELL HIM.
Something like "when confront the Emperor you will, beware, beware the corruptions of the Dark Side. Shoots lightning from his fingers, he does." You don't think Luke would have taken his training more seriously if he knew that some wrinkly old badass could shoot lightning at him? Yoda's folly nearly doomed the universe - 1) for underestimating and failing to defeat Palpatine in the first place, and 2) for not properly training Luke to face the challenges before him.
This, combined with the classic Skywalker temper, made Luke and Anakin's actions as depicted in Return of the Jedi probably the least probable scenario. This, I feel, is a more plausible outcome:
"And now, young Jedi, you will die."
With those words, Luke felt the lighting cascading over him become even more frequent and intense, if such a thing were possible. As if the initial volleys of force lightning shooting from Emperor Palpatine's fingertips were mere taunts. As Luke managed to glance up at the Emperor's wizened face through blinding light and his own tears, he saw not a look of fear, or intensity, but of contempt. Contempt towards Luke, contempt that a barely trained whelp could cause such damage to his prized enforcer, Darth Vader. Indeed, if word got out that a boy beat Vader to within an inch of his life, it would undoubtedly affect his reputation across the galaxy, a reputation that Palpatine would need years to reestablish. Years of sending Vader on missions that would prove a challenge, but not a danger.
The Emperor knew that Vader was but a shell of Anakin Skywalker's former self, and yet, his imposing image and his knowledge of the force still made him a formidable tool, allowing Palpatine continue to dwell in the shadows and focus on long-term plans. The Sith would again rule the galaxy under Palpatine, and Vader would be replaced most expediently. As long as the Jedi were in hiding, scattered and disorganized, Vader could withstand the challenges of a few poorly trained knights. But Palpatine knew that once the Sith ruled the galaxy, there would be more direct challenges, challenges that Vader would not be able to meet.
Vader himself had suggested turning the boy. Palpatine allowed that possibility, knowing that Luke represented, potentially speaking, everything that Anakin Skywalker should have been. Yes, there was the chance that father and son could try to overthrow the master, but Palpatine knew that was a fool's game. With Vader weakened and Luke untrained, he would be able to defeat them both.
What he didn't count on, was Luke defeating Vader so easily, less than three years after Vader took his hand and nearly his life. He had used his anger to strike down Vader, and Palpatine was excited at the possibility of a new apprentice. But when Luke threw down his weapon and purged the anger from his soul, Palpatine knew all was lost. He would not have a new apprentice, and Vader had proven himself unworthy. Still, Palpatine would repair him and have him soldier on until another could be found. For now, however, Palpatine was angry. Very angry. And that anger needed release. After showing Skywalker who the true master of the Force was, he would have Vader repaired and crush the rebellion.
Luke felt himself fading into unconsciousness, his own screams sounding dimmer in his mind. His body ached as the Emperor's Force lightning burned him from the inside out. He had never heard of such a manifestation of the Force. He had confronted and defeated Vader, using power he didn't know he had. Power drawn from anger, from fear, out of a desire for revenge. Power he knew he shouldn't have used, which was why he chased it out of his soul as quickly as it came. The vigour he felt as he chopped Vader down was gone, replaced only with pain. Pain, and questions. Why didn't Yoda warn him? Yoda had told him not to underestimate the Emperor, but how was he supposed to prepare for this? Was this his final punishment for not completing his training so many years ago? Luke had no way to defeat this enemy, and now all was lost. Some Jedi Master. Now, the galaxy would pay for Luke's mistake, and Yoda's pride. And why didn't Ben say anything? Twice now, Ben had misled him. Ben hadn't told him that Darth Vader was his father, and certainly didn't offer any enlightenment on how to defend himself against the Emperor.
The lightning somehow increased again in intensity and Luke would have screamed, if he had a voice. He wheezed for his father to help him, reaching out with love to the father he wished he could have known. To understand what events transpired to turn him into this angry shell of a man he had become. And Luke saw a common thread. Yoda and Ben had misled him - could they have misled his father as well? Did Darth Vader begin on a righteous path, only to be subtly twisted away from the light, and unable to count on his masters for clarity and guidance? Luke seethed internally. Yoda and Ben must have been afraid of the Skywalkers, afraid of the power they could wield, and set them up for failure. How foolish, when father and son could have been the two most powerful jedi, and brought peace to the galaxy?
Then, in his mind's eye, Luke saw it. The little dark ball of hatred, anger, resentment, fear. All he had to do was expand it, let it consume him. Ben and Yoda's ways had brought him nothing but pain and suffering. The darkness was dangerous, but without it, he would surely die. That fear motivated, strengthened him. He heard Ben's voice saying "Luke, don't give into hate", but willed it out of his mind with a blast of anger. How dare he lecture him now?
Luke, seeing no other way, allowed himself to be consumed by the raging inferno of anger, hatred and fear that was building inside him. He thought of Han, his sister Leia, Chewbacca, the droids, and all his loved ones that had been placed in danger because of Ben and Yoda's mind games and half-truths.
Time slowed to a crawl. Luke felt control return to his body. Though his muscles and tendons were flooded with electricity and spasming uncontrollably, the Force was moving his body now. Luke continued to focus on his hatred. Hatred for the Emperor, for Yoda, for Ben, for what his father had become. The lightning seemed to get weaker, and Luke seemed to get stronger. His body stopped shaking. He gathered his legs below him, braced his hands on the floor, and still being assaulted by the Emperor's lightning, he began to rise.
Palpatine was taken aback, but pleased. The boy had turned to the Dark Side to save himself. Now Palpatine could continue to open his mind to the possibilities of the Dark Side of the Force, and Luke would become his new apprentice.
"Your hate has made you strong, young Skywalker. You will make a fine apprentice."
Now it was Luke's turn to be taken aback. Was he becoming everything he feared? No. He wasn't becoming a monster. He still wanted to see the end of the Empire, still cared for his friends, still wanted to bring peace to the galaxy.
"I told you, your Highness, you've failed", he willed himself to say through gritted teeth.
Palpatine's anger burned hotter. He unleashed a barrage of force lightning as powerful as the flurry that felled Yoda. Luke grunted and swallowed hard, tasting blood. But his anger made him feel aware of everything, gave him vision through the Force. He saw his father standing at the Emperor's side, feeling conflicted and humbled. Seeing his opportunity to earn a reprieve, Luke focussed on his weakened father and pushed with the Force, feeling gratification as Vader toppled into the Emperor, knocking the old man off balance and disrupting his concentration.
Luke's anger gave him control over the Force like he had never experienced before. It coursed through his body, healing his wounds and warming his organs to keep him from going into shock. His eyes felt so open that he thought they would fall out of their sockets. Everything moved so slowly and predictably. He could see everything that was to happen. As the Emperor regrouped and unleashed another barrage of lightning, Luke was no longer afraid. All he had to do was concentrate his anger into his hand and hold it up.
The Emperor's lightning shot into his open palm, but it did not burn. Instead, it only further increased his awareness of the Force. Luke was absorbing the Emperor's lightning. The problem was that he felt as though he was overflowing with the Force, and needed to release it.
The Emperor's eyes widened with fear. Skywalker was more powerful than he ever imagined, and he was no longer certain he could control him. That moment of uncertainty would prove his undoing.
He stopped and looked and Luke, who had become a swirling maelstrom of Dark Side energy. He seemed six inches taller, and his eyes glowed yellow, his face that of a hardened warrior. Luke's voice, augmented by the Force, boomed through the control room:
"Enough! Now, it's my turn."
Luke screamed as the lightning he absorbed shot from the fingers of his non-bionic hand, blackening the tips. Palpatine's surprise prevented him from erecting his Force shield and the lightning ripped through him. Palpatine flew backwards, and realized too late where he was headed. He careened into the reactor core, unable to regain his composure as his body twitched and convulsed under the power of his own Force lightning.
Luke turned to face his father, who was again struggling to get to his feet.
"You can't die, father. You have so much to teach me."