According to Star Wars Legends content, the first Sith was a former Jedi Master, Ajunta Pall, who became a so-called Dark Jedi, or “Fallen” Jedi. As the name implies, these Force-sensitives chose to practice the Dark Side, and rejected the Light Side of the Force.
As the first Dark Lord of the Sith, Ajunta Pall founded the first Sith Empire and expanded it onto other worlds.
The original Sith were a humanoid species native to the planet Korriban in the Outer Rim territories. They were distinguished by their red skin, bone spurs, and facial tentacles. More importantly, the species as a whole had a predisposition toward the dark side of the Force.
The very first Jedi in Star Wars canon is a nameless figure known as the Prime Jedi. He was likely the builder of the first Jedi Temple on Ahch-To, seen in The Last Jedi. According to the Star Wars: The Last Jedi: The Visual Dictionary, the mosaic of stones in the chamber of the Temple depicts the Prime Jedi.
The Sith originated in a species of Force-sensitive warriors who discovered the efficacy of passion as a tool to draw on the Force at least 5,000 years prior to the events of the first Star Wars film.
Even though Kylo Ren uses a red lightsaber, harnesses the dark side of the Force, and wears a cape, he is not a Sith. Because of that, he can never hold the title of Darth. Instead, he was just a chaotic mess of the dark side (until he eventually found his way back to the light).
All too often, squabbling Sith in their bid for power upended carefully laid plans. After the Sith were decimated by the Jedi Knights of a thousand years ago, Bane enacted the Sith rule of two: there would be only two active Sith at one time -- a Dark Lord to embody the power, and an apprentice to crave it.
Jedi Master Yoda is the most powerful of them all. This should come as no surprise, as he was the head of the Jedi Order in the prequels and was revered for his abilities during the original trilogy. Yoda's power is unmatched and was a real threat to Darth Vader and the Imperials.
Obi-Wan Kenobi
Through it all, Obi-Wan reveals himself to be one of the very best examples of what a Jedi Knight should be: selfless, kind, and willing to do whatever it takes to protect those in need.
N'Kata Del Gormo was a Force-sensitive male Hysalrian Jedi Master who lived during the times of the Galactic Republic. According to legend, he found and trained Yoda and a Force-sensitive Human friend.
Truly, the most powerful Sith Lord was Darth Sidious, better known in his public persona of Chancellor (later Emperor) Palpatine. Through cunning and manipulation, Sidious killed his master to claim the mantle of Dark Lord of the Sith.
Historical information
The One Sith, also known as the New Sith Order, was a sect of dark side warriors and devotees founded by the self proclaimed Darth Krayt that followed a revised doctrine of the Sith ways.
The average lifespan for a Sith, without any assistance from medical technology, is around 250 years. Taking into account that Force sensitive beings have extended lifespans, most Sith can reach up to 400 years.
DARTH SION : THE IMMORTAL SITH LORD WHO MASTERED PAIN AND DEATH Star Wars Theory. DARK SIDE FRIDAY - Darth Sion is definitely one of the most powerful Sith Lords. Sion's deep pain and rage channeled the Dark Side allowing him to cheat death.
Darth Shain, headmaster of the Korriban Temple, took notice and convened with the Dark Councilor and Dark Lord of the Sith Darth Shane McMahon, who decided to confer the title of Sith Lord to the young apprentice at the age of 11, making him the youngest Sith Lord in the history of the Sith.
But one Jedi stands above the rest and needs to start getting recognized as the greatest Jedi who ever lived. That is none other than Obi-Wan Kenobi. While this saga is ultimately the story of the Skywalkers, Obi-Wan is arguably the best and most pure Jedi to ever come out of it.
Anakin Skywalker is the son of Shmi Skywalker, born without a father through the Force. He is the secret husband of Padmé Amidala, the father of Luke Skywalker and Leia Organa, the father-in-law of Han Solo, and the maternal grandfather of Ben Solo.
Obi-Wan Kenobi, during his confrontation with Vader on Mustafar, stated that he believed Anakin was indeed the Chosen One, but that his destiny had been altered, and the prophecy left unfulfilled. Anakin fulfills the prophecy by killing Palpatine. Skywalker's sacrifice brings balance and redemption.
#1 – Yoda. Yoda is widely considered to be the greatest Jedi of all time, and with good reason. He is a master of the Force, a skilled warrior, and has an unmatched wisdom that comes from centuries of experience. He is the embodiment of what it means to be a Jedi, and his legacy lives on long after his death.
He died of old age on Dagobah. Fans of Jedi Master Yoda likely know that he retains much of his power even after passing into the Living Force.
The second time Yoda mentions his long life is in Return of the Jedi, when he tells Luke, “When you reach 900 years old, you will not look as good as you will.” If we take Yoda at his word, that means the Jedi Master died at the ripe old age of 900.
At the end of the clone wars it is made clear that yoda has knowledge of Darth bane and that he created the rule of 2, surely they could only know this if a Sith told them or they learnt from a Sith holocron which requires a dark side user to open which poses the questions: who told them? or who opened the holocron?
The Sith stayed in hiding for a thousand years, their survival unknown to the Jedi, as they continued their revenge against the Jedi through Bane's Grand Plan. With Sith teachings passed down by Bane's Rule of Two, the Order managed to survive.