So, a Gray Jedi typically has the superior immediate strength of a Sith, maybe with less chance of “burning out,” to put it lightly (or burning up, in Anakin's case). However, they still don't fully come to the full, long-term victory of the light side.
That said, Vitiate, sometimes better known as the Sith Emperor, is often thought to have been stronger than Darth Sidious thanks to his mastery of the Dark Side of the force which granted him a ridiculously long life.
As the first Dark Lord of the Sith, Ajunta Pall founded the first Sith Empire and expanded it onto other worlds. The Sith took over the planet Ziost and created it as their capital and as Pall's new home.
Anakin Skywalker could have thwarted Darth Sidious and in fact did, albeit almost 25 years after he was given the initial opportunity. Anakin fell into Sidious' trap and attacked Windu, as Sidious played victim, only to then spring to life and fire lightning upon Windu.
Yoda will most likely win in a fight against Darth Vader because he is more skilled with a lightsaber and has the experience and feats that allow him to trim whatever size and strength advantage Darth Vader has over him. In fact, Yoda nearly defeated Palpatine, something that Vader could never do.
Yoda was tempted by the dark side on a few occasions throughout his life. If he fell to the Sith ways, he would've been more powerful than Palpatine.
Master Yoda has risen above all others to claim the top spot as the most powerful Jedi of all time and the true chosen one according to IGN's audience. He won pretty handily as well, as he was victorious in 89,756 of his 95,243 battles and had a win percentage of 94.2%.
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.
Within the Star Wars Legends continuity, Yoda's Jedi instructor was N'Kata Del Gormo, a Hysalrian Jedi Master, according to an in-universe legend.
Emperor Vitiate was a Sith Lord who successfully gained near immortality by draining the life force of an entire planet, later attempting to drain all life in the galaxy, which would give him true immortality.
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).
again… One of the main reasons why Yoda would've won against Anakin is simply because he was far better trained than him. Yoda could see the moves his opponents were going to make before they made them; therefore, battling against Anakin would've put him at a far heavier advantage.
Sidious may have given Dooku the title of Darth Tyranus, but because the Jedi Order knew him as Count Dooku, greatly preferring to not indulge his role as a Sith, they continued to call him by that name.
After a lightsaber duel against Maul and Savage, Sidious easily kills the latter, enraging Maul, who briefly holds his own against Sidious, but is ultimately defeated. Sidious proceeds to torture Maul with Force lightning, but spares his life because he has other uses for him.
If Obi-Wan had fought Sidious, he would have died. That has been well established, but I think Yoda was more concerned with the fact that Obi-Wan needed to face Anakin. Yoda wasn't sure if he could even beat Sidious, but he knew he could keep Sidious distracted from their fight.
Sidious was able to take on his previous apprentice and the apprentice of the apprentice. Sidious was able to defeat three master Jedi with ease but the battle would come down to who was stronger with the force and that contest is way to one sided in favors of Luke.
With Bane's defeat at the hands of his apprentice, Darth Zannah, allegedly on the Inner Rim planet of Ambria, the Jedi wrongly believed that the Sith were defeated with him, as the galaxy entered a millennium-long era of peace.
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.
Hakagram Graush, last King of the Sith, first appeared in the second issue of the 1990s comic book series Star Wars: Tales of the Jedi. The monarch went unnamed in the series, and his identity was only revealed in 2012, with the publication of Book of Sith: Secrets from the Dark Side.