If luke skywalker killed his father darth vader on the second death star, what would have happened? Would he have really turned to the darkside of the force, consumed by his hatred and his anger? Suppose he did. Would he have still been on the rebel's side, or would he have defected and joined the galactic empire? Turning to the darkside and becoming a dark lord of the sith are not synomynous with each other. They are interconnected with each other, but not synomous; they are not the same thing. All Sith are darksiders, but not all darksiders are Sith. All Sith lords want political subjugation, ie, in other words, meaning a very brutal and tyrannical dictatorship, because of their religious teachings. If Luke had turned to the darkside, he would've possibly wanted to rule an empire for himself. Maybe, but maybe not. Assuming that luke would have seized the imperial throne for himself, rather than staying on the rebel good guy's side, there are a few possibilites
He either would have joined emperor darth sidious/palpatine, or he would have probably killed the emperor and actually become the emperor himself. Emperor Luke Skywalker/Darth Something. Because, the reason for that is-the darkside of the force gives you a desire, a lust, for more and more power. While not all darksiders will end up being dictators, if a person who has converted to the darkside of the force is in a situation where those types of things are right there and available to him, such as an imperial army willing to find a new leader, or an emperor who wants you to become his apprentice right hand man/2nd in command, his greed, and his strong desire and lust for power would obviously to motivate him to do that. I think that a combination of both theories would've been true. Luke would temporarily be the emperor's sith apprentice (his 4th one, actually), and after a certain amount of time, he would have overthrown darth sidious, but he would have worked
Now, regardless of whether or not Luke would've killed the emperor and taken the throne for himself or become the emperor's right hand man (taking his father anakin skywalker's place), i am very curious as to speculate on what type of a ruler and leader luke would have been? I guess that he would probably use the second death star to destroy many imperial planets, as it was fully operational by that time. He would've ruled a tyrannical dictatorship. As to what type of atrocities Emperor Luke would have commited, I cannot say for sure in detail-other than blowing up planets with the death star (the main evil thing, actually), he would've done very similar things like the imperial atrocities commited in the Expanded universe. But there are other, far more interesting things that I find about this hypothetical situation.
The rebels would have lost the war if luke turned to the darkside. Why am I saying that? Well, suppose when darth sidious says "now fullfill your destiny, and take your father's place at my side", luke actually kills darth vader, he gets a sith lord baptism/knighting ceremony, similar to anakin skywalker's knighting/baptism as darth vader in episode 3 ROTS, the Emperor, knowing that the shield on Endor was being penetrated by the rebels, escapes from the second death star, and when the death star explodes, both luke skywalker and darth sidious escape from it. Darth Vader actually was the one who defeated the Galactic Empire. He was an important tool for the rebels, ironically. If luke skywalker became a sith lord, the emperor wouldn't have been distracted by torturing him and zapping him with the sith darkside force lightning, and he would've escaped. With their leader dead, the empire lost. With their leader, they don't lose. Even if the death star explodes and all of the military officials and leaders of the empire die, as long as the emperor lives, one tool of the puzzlepiece is still there.
Maybe Im wrong and the emperor overstimated the power of the rebels, and he would've died on the death star anyway. I don't remember that paticular part of the movies. But that kind of cheapens the whole idea of "a new hope" or the "chosen one", because that means that lando/wedge kills the emperor and wins the war against the empire/the sith, not the force sensitive users. Luke and leia were the last hopes of the rebel alliance because they had the light force powers to defeat darth vader and the emperor, two force users. They were expected by obi wan kenobi and yoda to be the new "chosen one(s)". But they were wrong all along. Darth Vader was the "chosen one" the "a new hope" of the galaxy. My point is, the emperor not knowing about the death star exploding cheapens that concept. And if luke turned to the darkside, the galaxy and the rebels were doomed. If the emperor would've died anyway, then the rebels would've won anyway, and the importance of that moment would lose its entire meaning.
Also, Im curious as to if luke would've become a "darth (fill in sith lord name)". Feel free to speculate here! This is a speculation, hypothetical discussion.