Amedda was one of the few beings in the galaxy who knew Palpatine's secrets, most notably his true identity as a Sith Lord.
Did Count Dooku suspect or even know that Senator Palpatine and Darth Sidious was the same person? Dooku knew Palaptine was Darth Sidious, he tells as much to Obi-Wan in Episode II.
Like the Jedi, the Sith became something of ledgend. Now, those who knew he was a Sith Lord: Dooku, Vader, maybe Tarkin, Yoda, royal guards, Mas Ameda, Maul, Plagueis, Mace Windu and co, Obi-Wan - off the top of my head.
Did you know that Palpatine was secretly Sidious in the prequels? Yes. During the OT his name and past as a senator was revealed. Then in ESB and RotJ we saw that he was a Force user.
The Guards were also among the few beings in the galaxy whom the Emperor trusted with the knowledge of his secret identity as a Sith Lord, knowing they would speak of it to no one, not even among themselves.
Count Dooku - himself revealed to be a Sith Lord - revealed to the captured Jedi Knight Obi-Wan Kenobi on Geonosis in 22 BBY that a Sith named Darth Sidious held influence over several senators in the Galactic Senate; it was the first such time that the Jedi learnt about Sidious in name.
This information comes to light form the comic series Darth Vader: Dark Lord of the Sith by Charles Soule and Giuseppe Camuncoli, in particular issue #7. Palpatine admits to Darth Vader that the Jedi he actually feared most was none other than Jocasta Nu.
Jedi Masters Mace Windu, Kit Fisto, Saesee Tiin, and Agen Kolar confronted Chancellor Palpatine upon learning of his secret identity as a Sith Lord.
If Maul knew, he would have tole Obi Wan or another Jedi during the Clone Wars. Dooku knew Palpatine was Sidious as he told Obi-Wan about him controlling the senate and referred to him as the dark lord. There's no real way of actually knowing if he knew ab palpatine.
Darth Maul died during a final battle with Obi-Wan in the Rebels TV series, and Palpatine couldn't have cared less. For him, finding and killing Maul for his failure simply wasn't worth the effort.
Thought dead, Darth Maul survived his injuries by focusing on his hatred of Obi-Wan Kenobi, the Jedi who cut him in half. His shattered body was dumped amid the refuse of the junk planet Lotho Minor, where the once deadly warrior fell into madness, staying alive on a diet of vermin.
To give a quick answer, Dooku didn't reveal Palpatine because he was still a loyal Sith apprentice and wanted to be a part of Palpatine's vision for the future. Dooku wanted to be his second in command and was willing to put his life on the line to manifest that.
the novel tarkin, written by James Lucino, confirmed that Grand Moff Tarkin. knew the true identity of Darth Vader. having identified anakin's lightsaber skills, military strategy, and interactions with his stormtroopers and the Sith, he was smart enough to not.
He also knew that Anakin had been corrupted by the dark side of the Force, and he wanted to spare him from any further suffering or guilt. By not saying anything when Anakin was about to execute him, Count Dooku showed mercy towards his former apprentice and allowed himself to pass away with dignity.
Amedda was one of the few in the galaxy who knew Palpatine was a Sith Lord, and assisted the Chancellor as Speaker of the Senate, helping him manipulate Senators into granting him more and more power.
DARK SIDE FRIDAY - Did you know Palpatine feared Qui-Gon Jinn? Palpatine was immensely powerful and he could see the future which made him very confident about pretty much anyone who stood against him. So why Qui-Gon Jinn?
Qui-Gon Jinn was more attuned to the Force than any other prequel Jedi, and that's one reason why Emperor Palpatine needed him dead.
In the final days of the Clone Wars, Windu turned to Kolar again, calling on him, Saesee Tiin and Kit Fisto to arrest Supreme Chancellor Palpatine. Confronted by the Jedi, Palpatine threw off his guise and revealed himself as Darth Sidious. He ignited his crimson-bladed lightsaber and struck down Kolar.
In non-canon material it is said that Palpatine had a number of concubines and never took a wife in fear that he would produce a legitimate heir. One of these non-canon concubines was Roganda Ismaren, a former Jedi who survived Order 66, and lived for a time at Palpatine's side.
First on the list of Palpatine's rivals is Darth Bane. He was not only unrivaled with a lightsaber in his day, but he was also a master at shrugging off the force powers of others, Sith and Jedi alike. As the sole surviving Sith of the Jedi-Sith War, his knowledge of the force should not be underestimated.
Even after his brutal scorching in the fires of Mustafar, sand remained the only natural phenomenon that Vader feared. To him, sand was a reminder that he'd failed to save his mother or Padme from death.
As powerful as Darth Sidious may have been, it's easy to forget he actually seemed afraid of Master Yoda. As seen in Revenge of the Sith, Palpatine initially thought he could deal with the aged Jedi Master - and then, when Yoda proved able to counter the Sith Lord's Force lightning, he fled.
Bottom line, Dooku never considered himself a Sith. And he wasn't; he was a man looking to change the galaxy in a way the Jedi were unwilling to try. And that is why he joined the Sith and became Darth Sidious' apprentice, Darth Tyrannus. When Dooku became Sidious's apprentice, he was already an elderly man.
Yoda. Yoda was a wise, experienced, and powerful Grand Master of the Jedi of an unknown species and the oldest known prophet in existence (having lived at least 900 years), considered the wisest and most powerful Jedi Master within the Star Wars universe.
Yoda didn't specifically know how this would go down, or to what degree Anakin would cause it to happen, but he was playing a much longer game by Revenge of the Sith, and that's at least, in part, explained by Yoda's Force connection with Qui-Gon's spirit.