I think Nihilus would easily beat Revan if they ever fought - not due to skill or strength, but because as Kreia said, "There are techniques within the Force against which there is no defence".
The Exile was probably the only person that could defeat him, which is why Kreia lured him to Telos in the first place. Because the Exile was also a wound in the Force, Nihilus could not drain her. And because he had no Jedi to feed off of on Telos, he was much weaker then he normally would have been.
There is no character is all of star wars who could beat him beside the exile. So while I do agree that Nihilus is the most dangerous thing..... Ever. He is not the most powerful I have to agree that Sidious is by far the most powerful Sith Lord and second most powerful Darkside practitioner ever.
What if Darth Nihilus Returned During the Clone Wars? Full Fan Fiction
Who is more powerful than Darth Nihilus?
The only KOTOR 2 character more dangerous than Nihilus is his former master. Kreia has spent time as both a Jedi and a Sith, using her knowledge to instruct prominent figures like Nihilus and Darth Sion. Of course, this has equipped her with life draining and other dark abilities.
However, Revan and Malak eventually found their way to Dromund Kaas and discovered that the Sith Empire indeed still lived. Their attempt to eliminate the Sith Emperor went horribly wrong, with the Emperor dominating their minds and finally turning them to the dark side.
Summary. Jar Jar Binks's clumsiness may not be genuine, but rather an act to disguise his true nature as a Sith Lord infiltrating the Republic. Palpatine carefully orchestrated events to manipulate the galaxy, and Jar Jar's involvement suggests he may have been the eyes and ears on Naboo.
The obvious answer is Darth Vectivus, a Sith Lord who lived in his house and didn't try to conquer the galaxy or destroy the Jedi. And while he wasn't evil, he wasn't good, either. However, there is one good Sith. That would most likely be Darth Vectivus.
Sidious is probably more powerful than Nihilus. However, that does not mean that Nihilus cannot power through him with his force drain. Force drain takes away someones ability to use the force and eventually your life force too.
Darth Nihilus was a Human male who reigned as a Dark Lord of the Sith during the era of strife following the Jedi Civil War. Before becoming a Sith Lord, he lost everything during the Galactic Republic's war against the Mandalorian Neo-Crusaders.
Revan's lightsaber skills must also not be ignored. Therefore, considering both experience and powers, a Jedi Revan at the height of his powers could flair well against Palpatine in a fight.
Darth Sidious, also known as the Emperor and Supreme Chancellor Palpatine, is not just the evilest Sith in Star Wars (arguably in both canon and Legends) but the evilest villain overall, deemed so thanks to his irredeemable actions throughout the Skywalker saga and surrounding content.
While Darth Sidious mastered the Dark Side and ruled over an Empire for two decades, Vitiate (or Valkorion) went even further, rebuilding the Sith Empire and ruling over it for a hundred years while he embodied the Dark Side to be perhaps the most powerful and evil being in the galaxy's history.
While he was good with a lightsaber, this isn't what he was known for. Instead, Nihilus focused his work on understanding the mortality of existence, serving as a philosopher among the Sith. While Darth Nihilus may have been wise, he certainly was not stronger than Darth Vader.
Darth Gonk (Later Darth Wrife) was a force sensitive droid. He reigned during the first years of the Galactic Empire to the years of the Fel empire. He had a vast knowledge of the force that even rivaled the most powerful sith, such as Darth Sion and Darth Maul.
Although it's not fully clear where the Darth moniker originated, Darth Andeddu is thought to be the first character to use the title in-universe. Having originated in Legends, Andeddu was mentioned in the new canon in the comic Star Wars Adventures: Return to Vader's Castle 2, which referenced "Andeddu's flames".
Anakin Skywalker's birth mystery is solved - his mother, Shmi Skywalker, reveals that there was no father and she can't explain what happened. Qui-Gon Jinn believed that the Force itself created Anakin in Shmi's womb, making him the Chosen One who would bring balance to the Force.
Disney used Revan as an inspiration to create Kylo. His armor, inner conflict between Light and Dark and his use of the Force. Snoke considers Kylo to be the ideal embodiment of the Light and Dark sides of the Force, much like Revan, who was a master at both sides of the Force.
