Darth Vader doesn't fear the Emperor, he despises him, just as Vader so vehemently despises himself. So, if not Palpatine, who could Vader possibly fear? Well, the answer is deceptively simply, yet incredibly shocking all at the same time: Luke Skywalker.
Summary. Darth Vader's intense hatred extends beyond Obi-Wan Kenobi and himself to Emperor Palpatine, as revealed in Star Wars: Darth Vader #39. Vader had to tap into his deep-rooted hatred for Palpatine to overcome a deadly Scourge and destroy a Clone Wars-era droid.
Darth Vader was so feared because it didn't matter who, or how many, or where he faced anyone. Darth Vader destroyed and murdered his way through every situation that got in his way. Indomitable, inexhaustible, unfeeling and ruthlessly efficient. That's Darth Vader.
Darth Vader's Insecurities are His Biggest Weaknesses
In the end, virtually all who have made the attempt to use Vader's cybernetic nature against him have ended up dead or defeated. The elite few who have had the upper hand, even before his conversion to mechanical monstrosity, have done so by dominating him mentally.
The Opponent who Scared Darth Vader to his Core Unlike Anyone Else [Legends]
Who can beat Darth Vader easily?
While Vader had his weaknesses, including vulnerability to electricity, characters like Emperor Palpatine, Mace Windu, Yoda, and Obi-Wan Kenobi all had the potential to defeat him in battle.
Darth Vader's love and skill for droids and mechanics, particularly from his childhood, becomes a major tactical weakness for him in Star Wars: Dark Droids #3. The Scourge targets Darth Vader and attempts to defeat him by assimilating his own droids, but their plan is foiled by outside interference.
While Darth Vader and Grand Admiral Thrawn only crossed paths a handful of times, the two men had great respect for one another. Unlike the other high-ranking officers in the Imperial Army, Thrawn never showed any fear of Vader, and Vader respected him for that.
Vader's one friend he trusted the most was Erv Lekauf, the Dark Lord's personal adjutant. After he was heavily injured in a fire, Lekauf was force to retire. Erv's bravery, honorable, responsible, personality gave Vader his respects and the two saved each others' lives a few times.
While Vader could sometimes show compassion to his soldiers, this compassion was far outweighed by his cruelty. Due to ghost stories like "The Predecessor," any disappearance or mysterious death within the Imperial Army could possibly be attributed to Vader, even when he had no hand in the events.
Erv Lekauf was a lieutenant in the Imperial Army who served as Darth Vader's personal aide for several years. On a mission to Vohai in 19 BBY, Lekauf helped Vader fight the Emperor's Hand Sa Cuis, impressing the Dark Lord with his courage and loyalty.
Since he was that little boy, Anakin has feared the “death” dragon. The dragon inside of him that reminds him that stars burn out, that people will die, that all things die. This is the kind of fear that lives inside Anakin Skywalker: the dragon of that dead star.
Some time later, he faced the Sith Lord Darth Vader. Infil'a put up a fierce fight against Vader, almost killing him by throwing the already damaged Sith Lord off of a cliff. Despite severe damage to his suit, Vader survived the fall, and repaired himself with parts from Infil'a's droid, Arex.
In Star Wars Legends and Canon, Galen Marek (Starkiller) is the only Jedi (other than Obi-Wan Kenobi) to put a beat down on Darth Vader/Anakin Skywalker. Galen was secretly trained as a Sith Lord apprentice to Vader, but returned to the light side and the Jedi.
The very notion that Darth Vader would hold onto his respect for Tarkin shows that all of Anakin Skywalker's memories have not gone to the wayside as a result of his turn to the dark side.
In a documentary for Star Wars: Revenge of the Sith, George Lucas strangely states that Emperor Palpatine is the hero in his own story and a well-intentioned extremist. However, the film itself doesn't imply this at all, so Palpatine still counts as Pure Evil.
Yes, they were afraid of each other. In fact, that's the whole relationship between a Sith master and their apprentice. As Darth Bane, the founder of the Rule of Two (the same rule that Palpatine ironically broke) said: "Two there should be; no more, no less.
Ahsoka's Baylan Skoll knew that Darth Vader was Anakin Skywalker, a secret that very few people in the galaxy were aware of during the events of the latest Star Wars show.
In a Vanity Fair interview from 2005, George Lucas went deeper into why Anakin became much weaker as Vader. In the interview, he explained that because Anakin's limbs were severed and replaced by robotics, it was harder for him to use the Force than it was before his battle with Obi-Wan.
