There are plenty of powerful and vile Sith in the world of Star Wars, but Darth Sidious was on a different level than most of them. His power level was unprecedented, and his foresight was legendary. After the Sith remained hidden for a thousand years, Sidious emerged to destroy the Jedi Order and establish the Empire under his rule. Although he may get a bit too much credit for everything that happened to Anakin, he was certainly one of the more manipulative villains of the Star Wars Universe.
In addition to all the Jedi he murdered and the innocent people that he harmed, Sidious ruined the lives of all his apprentices. He turned Darth Maul's life into an utter tragedy and manipulated the powerful Darth Vader in addition to repeatedly humiliating Count Dooku. Because he wasn't as powerful as Vader or as flashy as Maul, the count typically gets less attention than Sidious' other two apprentices; however, Dooku felt the brunt of his Master's manipulative power more than once.
The most well-known time that Darth Sidious embarrassed Dooku was in the film Revenge of the Sith. Anakin and Obi-Wan arrived at the Invisible Hand to rescue Palpatine, and were confronted by the count. While he was able to incapacitate Obi-Wan, Anakin proved to be much more of a challenge, with his power having increased exponentially since Attack of the Clones. The future Darth Vader disarmed the Sith Lord by amputating both of his hands before decapitating him at Palpatine's prompting.
Although this is what was clearly seen in the film, there appears to now be another side of the story. According to Matthew Stover's Revenge of the Sith novelization, Dooku believed that he was going to survive the confrontation with Anakin. Sidious previously convinced him that the "plan" was to kill Obi-Wan and turn Anakin to the Dark Side. After being taken into custody, Dooku would renounce the Confederacy and help the Republic win the war. When all of that was finished, they would have formed an empire, commandeered the Jedi Order, and ruled the galaxy as an order of Force wielders.
Of course none of that happened, and Dooku realized too late that his master had betrayed him. The apprentice was instead used as bait to lure Anakin to the Dark Side, and was then abandoned to a grisly fate. However, this was not the first time that Sidious had humiliated Dooku in order to achieve a grander purpose. That came in the Son of Dathomir comics.
The four issue series told the tale of what happened after Sidious captured Maul at the end of the Clone Wars episode "The Lawless." In short, Sidious allowed Maul to escape in order to successfully lure out Mother Talzin, who was then killed by General Grievous. But this was not the future Emperor's only manipulative action.
First, Sidious allowed Dooku be captured by Darth Maul. Then, after temporarily joining forces with Maul, the Sith apprentice was possessed by the spirit of Mother Talzin. The witch needed a body to drain so that she could manifest in the flesh, and it's a wonder that Dooku survived the processl. At the conclusion of the comic, the count attempted to apologize for allowing himself to be captured and letting Maul escape. However, Sidious reassured the count that everything had proceeded according to plan, which was to ensure that neither Maul nor Mother Talzin would never be legitimate threats again. This, along with his equally reprehensible actions in Revenge of the Sith indicate that Sidious has never cared about the well-being of his apprentice and has always seen him as an inconsequential pawn.
