Dooku couldn't beat Sidious. Even Dooku knows his place being unable to defeat Sidious - that is why he never tried to overthrow him. Dooku has also tried to raise padawans of his own (twice) in an effort to overthrow Sidious.
Despite Dooku's skill and intellect, he wouldn't have been able to successfully overthrow Palpatine with any of his dark side apprentices in canon or Legends.
That notwithstanding, Master Windu was also one of the best. If the two spared as Jedi, Dooku would probably win the match because he was the better all-around duelist.
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.
Overall, Dooku was far more equipped to become a Sith Master than Maul was. Had he managed to overthrow Palpatine, Dooku would have been able to use his position, combat abilities, and dark side Force powers to take his place on the throne Palpatine had carved.
Why Sidious Was TERRIFIED of Dooku After Dueling Yoda - Star Wars Explained
Could Rey beat Count Dooku?
7 Why Rey Couldn't Win: Dooku's Skills Far Outshine Rey's
Rey was able to triumph over a lot of foes through sheer pluckiness and a good mixture of luck and sheer Force power. That won't help her against Dooku.
Yoda was winning between their duel why still in the light side of the Force. Meanwhile, Mace had to turn slightly to the dark between the duel between him and Sidious to win. Yoda on the other hand, didn't turn dark. So, this proves that Yoda is far more stronger than Sidious or Mace Windu.
In the canon timeline, Mace Windu is known as the Jedi Order's greatest champion. With this in mind, it's easy to understand why Mace is one of the few beings capable of defeating Palpatine.
Dooku couldn't beat Sidious. Even Dooku knows his place being unable to defeat Sidious - that is why he never tried to overthrow him. Dooku has also tried to raise padawans of his own (twice) in an effort to overthrow Sidious. The first time, Assage Ventress grew too powerful so Sidious ordered her d…
More than a strategic retreat, Count Dooku running away from Yoda is a reminder that Dooku is far less powerful than Yoda. Dooku could have not beaten Yoda in Geonosis, meaning that the fight would have ended with Dooku either killed or captured had it continued.
It's hard to say exactly how the fight happened, as this is a comic, and the amount of movement shown is very minimal. There are, however, some important things to note. While it's clear that nobody won this duel, Dooku definitely had the upper hand in the end.
Kenobi would and has lost to Count Dooku on multiple occasions. This was primarily demonstrated through the prequel movies, where he was overwhelmed in Attack Of Clones and defeated in mere seconds on the Separatist flagship during Revenge Of The Sith.
It's already been shown in the source material… more than once… that Darth Maul is not on Darth Sidious's level. Every time he dueled Sidious as his apprentice (in Legends) he got easily defeated.
The term “gray Jedi” in Star Wars is somewhat of a misnomer, considering that the definition refers to one who is practically non-Jedi. That being said, quite a few Jedi can be placed into this category. But Mace Windu identified as a Jedi despite his possible inclusion in the "gray" category.
Mace does have some advantages, for example shatterpoint and Vaapad. However, even with these advantages Windu would be defeated by Vader. The Dark Lord is one of the best duelists in canon, slightly more superior than Palpatine to the point that even Palpatine indicated Vader's strength and power.
While little is known about Yoda's species, we do know, however, that they're incredibly gifted in the Force. Both Jedi Master Yaddle, and now Grogu, hold great Force powers, but no Jedi Master has ever held greater power than Jedi Master Yoda.
Dooku knew Palaptine was Darth Sidious, he tells as much to Obi-Wan in Episode II. Remember whe he's holding Kenobi as his prisoner? dooku tells Obi-Wan the Senate was being controlled by a Sith Master, remeber also the look Dooku shoots at Palpatine when he orders Anakin to kill Dooku.
Dooku's vision for the Empire was superior to Palpatine's, as he aimed to transform the Jedi Order into an unstoppable Sith Army. His talents as a Force wielder, though outclassed by Palpatine and Yoda were also top tier, as nearly all Jedi were unable to withstand him.
