As the ultimate villain of every Star Wars trilogy, Palpatine has hundreds of atrocities to his name. His plots and machinations toppled the Republic, ended the Jedi, and threatened to drown the stars in fire and blood unless the entire galaxy submitted to an eternal Sith Empire. Everything he did was in his own interests.
While everything he did was evil, some of his actions stand out as crueler than others. Whether it's because they're gratuitous, deliberately made to be as torturous as possible, or simply unnecessary, certain things Palpatine did truly stand out above his general plans.
10 Sending Kylo Ren On A False Quest To Kill Rey
At the beginning of The Rise of Skywalker, Dark Jedi Kylo Ren meets with Palpatine on the planet Exegol. The two form an alliance, with Sidious promising to give Ren control of the Final Order, a massive fleet of planet-destroying warships, in return for killing young Jedi Knight Rey, Palpatine's granddaughter.
However, as Palpatine's plans involve Rey reaching Exegol and killing him, it's clear that he never intended for Ren to succeed, and planned to use the fleet himself. Whether he intended for Kylo merely to distract Rey and the Resistance, or for Rey to kill him and hopefully slip closer to the dark side is unknown, but he forged an alliance only to send Ren to his likely death.
9 Ordering Count Dooku's Execution
Sidious is a poor ally to many of his subordinates. While some twisted affection may exist between him and his desired apprentice, Anakin Skywalker, and he expresses pride in the abilities of Darth Maul, he is callous and cruel to his apprentices, and not afraid to betray them.
Dooku is an evil man who is happy to plunge the galaxy into civil war to further his own interests, but when he is maimed and at Anakin's mercy, he strikes a surprisingly pitiful figure as Palpatine orders his execution. Clearing up loose ends and furthering Anakin's descent to the dark side, it is a cruel betrayal of a once-loyal servant.
8 Assaulting The Resistance Fleet With Force Lightning
At the climax of The Rise of Skywalker, Palpatine changes his plans from having his spirit inhabit Rey's body after his death, to instead ripping the energy from Rey and Ren's Force Dyad, and using it to empower himself and heal his broken form. From there, he uses the influx of energy to launch a massive blast of Force Lightning into the battle around Exegol, disabling and beginning to destroy the Rebel fleet.
Sidious is in effect preparing to kill hundreds slowly here, as their ships fail and collapse around them. The cruelty is limited by the fact that it is a pragmatic tactical move to swing a battle in his favor, but it is nonetheless vicious.
7 Goading Luke & Vader Into Fighting
It is ultimately owing to Palpatine that Luke and Vader have their famous lightsaber duel at the end of Return of the Jedi. Each wants to turn the other to their side of the Force without fighting, but Luke also wishes to kill the Emperor. Even as hateful towards Sidious as he is, Vader cannot just stand by while Luke does so, and so they fight.
Sidious watches the battle and goads both of them, urging them to give into the dark side and use their feelings of anger. It is clear that he is playing them off against each other, to ensure that he has only the strongest Skywalker for his apprentice, and is not afraid to make a father and son kill each other for that purpose.
6 Killing Mace Windu Slowly
Once Mace Windu learns that Palpatine is a Sith Lord, he reacts quickly, assembling a team of Jedi to arrest—and later execute—the Chancellor. A ferocious duel breaks out between Windu and Sidious, which ends with Windu victorious, and only the intervention of Anakin is able to save Palpatine's life.
Once Windu has his hand removed, Palpatine uses his Force Lightning on the Jedi, throwing him out of the window and to his death. Before he does this, however, he spends several seconds slowly torturing Windu with lightning first while Anakin watches, clearly enjoying the experience.
5 Putting Vader Through Agonising Life-Saving Procedures
Darth Vader is horrifically wounded after his duel with Obi-Wan Kenobi on Mustafar in Revenge of the Sith, having three of his limbs removed and being burned after his clothes catch fire. Rushing to his apprentice's aid, Palpatine ensures he won't lose his investment by having Vader operated on and forced into a life-sustaining suit.
However, he lacks the mercy to have Vader's pain dulled in any way, or Vader rendered unconscious. As seen, even simply having his clothes peeled from his skin leaves Vader screaming in agony, and there are days of agonizing surgery to follow. Palpatine hoped that the pain would strengthen Vader in the dark side.
4 Having The Separatist Leaders Butchered
Throughout the Prequels, Palpatine acts as both the leader of the Republic and the shadowy benefactor of the Separatist movement, publicly led by Count Dooku. He promises them that, once the war is fought, they will be left alone to govern themselves, free from the Republic and at peace.
Once Sidious wipes out the Jedi and assumes control of the Republic, however, the Separatists present a threat to his goal of a united Empire. So he has them gather on Mustafar to plan the next stages and then has Vader travel to the planet to massacre them. While ultimately villainous, these unarmed and frightened characters are still murdered in cold blood by an erstwhile ally.
3 Murdering Savage Opress & Torturing Maul
In The Clone Wars episode "The Lawless," episode villain Maul and his brother, Savage Opress, appear victorious over Obi-Wan Kenobi, having retained their power over Mandalore and murdered Duchess Satine Kryze. Then a shuttle approaches the planet, and Maul recognizes the presence of Sidious. Ultimately, Maul and Opress engage Palpatine in a fierce duel.
Deliberately echoing how Maul killed Obi-Wan, Palpatine takes great joy in separating the two brothers, before forcing Maul to watch as Opress is run through. After a frenzied denouement to their battle, Maul is left disarmed and pleading for mercy. Sidious reminds him that the Sith do not engage in mercy, and viciously tortures the already-grieving Sith.
2 Torturing Luke Skywalker To Death
The final battle of Return of the Jedi is more spiritual than swordplay-based, with the duel between Luke and Vader having as much to do with who can turn whom to their side of the Force as who can defeat the other with a lightsaber. Luke appears to win by refusing to kill the helpless Vader and throws his lightsaber aside as he rejects Palpatine and the Sith.
Palpatine responds by blasting Luke with Force Lightning in front of his own father, making it clear that he fully intends to torture the Jedi to death very slowly as punishment for his defiance. It is only Vader's intervention that sees Luke spared from an agonizing death.
1 Having Order 66 Carried Out
The masterstroke of Palpatine's plan to end the Republic and the Jedi comes at the climax of the Clone Wars, after the Jedi attempt to assassinate him and after he has turned Anakin to his side. Palpatine contacts the Clone Commanders and orders them to carry out Order 66, the destruction of the Jedi Order.
The end result is the Jedi, the galaxy's noble, compassionate protectors, butchered in their thousand by the very troops they were leading and had close bonds with. The cruelest depths of Order 66 come when Anakin and the 501st march on the Jedi Temple, killing all the Jedi there, including the young children.