Galen Marek, better known as Starkiller, was the main protagonist of the Legends games before Disney bought Lucasfilm. He displayed incredible control of the Force, from moving a Star Destroyer to defeating both Vader and Palpatine in succession.
Lord Starkiller is an antagonist in an alternate Star Wars timeline in which Darth Vader is defeated and killed by his former apprentice Galen Marek, code named Starkiller.
As Darth Vader, he was one of the strongest beings in the entire galaxy. But even then, he was never able to surpass his master, Darth Sidious. A Sith Apprentice can only become the master when they murder the one who trained them.
At its inception, the title and position was granted to Darth Vader. It seems that in this capacity, Vader's powers were those of Commander-in-Chief of all Imperial forces, answering only to Emperor Palpatine.
Obi-Wan Kenobi soundly defeated Vader in Star Wars: Episode III - Revenge of the Sith and Obi-Wan Kenobi, and is easily one of the most powerful Jedi Vader ever faced. Vader and Obi-Wan were similar in swordsmanship and Force-sensitivity, but Vader's hatred of Obi-Wan often caused him to fight irrationally.
Why Starkiller Was MORE POWERFUL Than Darth Vader and Sidious - Star Wars Explained
Did anyone outrank Darth Vader?
Vader Outranked only by Sidious - CON: The only thing I can find that says Tarkin outranked Vader is a quote by David Filoni in 2015 during an interview about Rebels. He actually says that Tarkin outranks Vader.
Kylo Ren is not weak, his potential is certainly as high as any of the Skywalker lineage, but I believe he simply has a misunderstanding of how the Force works, and because of this misunderstanding, he has made himself weaker.
Yep. Darth Maul didn't really say or show straight up that he "feared" Darth Vader, but he openly stated his belief that he could not defeat Darth Vader without the help of the Jedi, therefore on his own.
He is pretty powerful, definitely up at an A tier level of ability. He has faced quite a few potent Jedi masters. If memory serves, the most powerful person he beat outright was Shaak Ti. He did technically beat Vader, but he used lightning and then damaged his suit with a hurled piece of debris that exploded.
Darth Vader was Starkiller's master. He gave Starkiller tasks and missions to complete, and was hoping to use him to overthrow Darth Sidious and take over the Empire. But he was NOT Starkiller's friend or father figure. He was abusive, starving Starkiller and forcing him to fight when starved or...
However, Starkiller still managed to best Kenobi - defeating him in combat and causing his spirit to disappear with a blast of Force Lightning. Unable to battle Starkiller, Kenobi's spirit told Luke to run, with the Millennium Falcon fleeing Mos Eisley.
Starkiller shot Force Lightning at him and ended the fight as he threw his lightsaber at him, splitting Kylo Ren into two and launched his remains out of the base.
The fight itself is a draw, but Yoda turns it into a victory for Sidious by retreating (because they are evenly matched and there is nothing more he can do then and there).
And while his warnings don't work, at the very least, it shows that Maul became aware of Anakin and what he would soon become. With the rise of the Empire, it's likely Maul caught on to Vader's existence pretty quickly.
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.
Kylo lost to Rey in TFA because he was heavily wounded and was holding back against her due to Snoke's request that he bring her back to him alive. He is also stated by Palpatine in the Secrets of the Sith book to be “equally as powerful as a real Sith despite not being one”.
This caused him to attempt to assassinate him in his sleep. Needless to say, Kylo Ren is almost definitely a significant threat. However, we cannot definitively say that he is more powerful than Luke. Kylo's powers are vast but they are still highly unbalanced and difficult to control.
Had Vader and Snoke faced off against each other, Snoke's impressive Force abilities would have allowed him to defeat Vader with a mere flick of his fingers.
Vader knew that he could never defeat Palpatine by himself (especially after his master bested him on Exegol as well), which is why he tried to recruit Luke to help overthrow him during the Empire Strikes Back. He may have not been able to overthrow the Emperor, but he could throw him over the railing to save his son.
He just didn't have the allies to make it happen, explaining why he had relied on Luke to join him. Taking after his master, Vader evidently learned from the tragedy of Darth Plagueis the wise. Unfortunately, he just lacked the proper resources.
