Although we've only seen a few Sith lords in the Star Wars movies, there are plenty in the Star Wars comics, books, TV shows and games that have powers even greater than we ever got to see on the big screen.
By channeling the Dark Side of the Force, almost anything is possible, and with Episode VIII shaping up to be the darkest Star Wars film yet, it's possible we might finally get to see Kylo Ren harness the truly terrifying power of the Dark Side. And here's who he has to live up to.
Darth Bane appears in the Expanded Universe, and while most of this was declared non-canon by Disney, Bane's appearance in the animated show The Clone Wars saved him from being cast out of the canon.
The sole survivor of the Sith massacre, which occurred over 1000 years before the Star Wars prequels, Darth Bane is an incredibly powerful and very popular Sith lord. In fact, he was the one to instate the Rule Of Two which commands that there must only be two Sith at any one time. This fan-made trailer explains his backstory, and it's pretty cool, too.
Bane managed to stick around as a Force ghost long after he perished at the hands of the Jedi, causing all sorts of problems in The Clone Wars. Remembered as one of the most terrifying Sith lords, Bane definitely makes it to the top of this list.
Darth Plagueis was known as "The Wise" because he was very close to learning the secret of immortality. He could stop people from dying but unfortunately could not prevent his own death at the hand of his apprentice, Darth Sidious a.k.a. Palpatine a.k.a. the Emperor.
Darth Plagueis was first mentioned in the films by Palpatine, when he explains to young Anakin how Plagueis could prevent people from dying.
"Darth Plagueis was a Dark Lord of the Sith so powerful and so wise, he could use the Force to influence the midi-chlorians to create life. He had such a knowledge of the dark side, he could even keep the ones he cared about from dying."
Although Palpatine supposedly killed his master, with Plagueis's powers it's entirely possible that he could have survived this attempt on his life. And he might have been lurking in the shadows for years, waiting for his chance for revenge - which is the foundation for a popular fan theory that Supreme Leader Snoke is in fact Plagueis himself.
But we'll just have to wait until Episode VIII to find out about that.
Unfortunately, this Sith lord has been cast out of the official canon, as she appeared in the comics set after Return Of The Jedi. Although she's just a legend now, Maladi is still totally badass. Something of a mad scientist, Darth Maladi was the head of the revived Sith Intelligence and Assassination. She specialised interrogation, using her skills in science as well as her formidable Force powers to torture her victims.
Maladi is also one of the few Force users able to battle with lightning whilst engaged in lightsaber combat, making her a terrifying opponent, and one of the most powerful Sith lords we know of.
As the avatar of the immensely popular game Knights Of The Old Republic, Revan is definitely a fan fave, and a main contender for one of the most powerful Sith Lords in Star Wars' history.
"Savior, conqueror, hero, villain. You are all things Revan… and yet you are nothing. In the end you belong to neither the light nor the darkness. You will forever stand alone."
In the game, players have the chance to choose whether Revan will make choices for the Dark or Light Side, and Revan can also be male or female depending on the decision of the player. Ultimately though, he is known in the official canon as male.
Crossing over from the Light to the Dark and back again (depending on what choices the player makes), Revan is one of Star Wars' most interesting characters and undoubtably one of the most powerful Sith Lords, or Dark Sider.
Revan was trained as a Jedi, making him ruthless in combat as he knew all the Jedi's moves and what they would do next. He also learned many Mandalorian combat moves when battling and deposing their ruler, Mandalore the Ultimate. Revan's history is rich and interesting - he pretty much catalysied the Jedi Civil War, fighting against them as a most powerful Sith Lord, then later defected to the Jedi side as the result of a mindwipe. During his time as a Republic soldier, Revan left his Sith past behind him and was given the title of Jedi Knight, later Prodigal Knight for his bravery and efforts against the powerful Sith Lords.
But for all his efforts to fight for the Light, Revan's mission to kill the Sith Emperor (one of the most powerful Sith Lords of all time) failed, and he was imprisoned and tortured for three hundred years. This caused his mind to splinter, remembering snatches of his time as a powerful Sith Lord as well as a Jedi Knight. Although he was eventually killed by the Sith Empire and the Republic, Revan's legacy lived on through Darth Bane, who used his teachings to develop the Rule of Two.
Although she was never a Sith lord, Asajj Ventress was a formidable opponent for Anakin Skywalker and Obi Wan Kenobi as they fought in the Clone Wars. Training under Count Dooku and flirting with Kenobi at every possible opportunity, Ventress bested the Jedi on multiple occasions.
Ventress is interesting because of her history: she wasn't always an ally of the Sith lords, but started her life as a Nightsister witch on the planet Dathomir. Her relationship with her fellow Nightsisters was often tested throughout the show and expanded later in comic books. Ventress was orphaned and adopted by the Jedi Narec, but although they spent years protecting the downtrodden, Ventress was seduced to the dark side by the powerful Sith Lord Count Dooku when Narec was killed and she was orphaned yet again.
Ventress then became a commander for Dooku in the Clone Wars, fighting against the Jedi and clashing often with Obi Wan Kenobi and Anakin Skywalker (never suspecting Anakin would become one of the most powerful Sith Lords of all time). Eventually though, the character reformed in one of the show's most compelling arcs. In her last act, she absorbed the lightning blast meant for her lover, proving herself a badass even in death.
Finally, an article about the darkest Dark Siders wouldn't be complete without the formidable Inquisitors from Star Wars: Rebels. Assembled by the Emperor to wipe out any Jedi who survived Order 66, the Inquisitors relentlessly pursue our heroes throughout the galaxy.
The Grand Inquisitor is especially terrifying, although he was eventually defeated in the season 1 finale. The Inquisitors add a sense of scope to the Dark Side, revealing that evil is not confined to the Sith lords. Although the Inquisitors were presumably defeated sometime during the original Star Wars trilogy, it would be great to see a remnant of this order pop up in the new era of Star Wars films.