A small detail in Star Wars: Episode III – Revenge of the Sith suggests that Palpatine toyed with the idea of killing Anakin—before he had fully seduced him to the dark side. Ever since meeting the Chosen One in The Phantom Menace, Palpatine molded Anakin into his idea of the perfect apprentice. Given that Anakin was immensely powerful with the Force, Palpatine knew that he would be an essential piece of his master plan to rule the galaxy. In Palpatine’s mind, having Anakin by his side was his final blow to the Jedi. Even so, he was wise not to hang his entire plan on whether Anakin turned.
In an early draft of Revenge of the Sith, Lucas toyed with the idea that Palpatine engineered Shmi Skywalker’s death—further pushing Anakin toward the dark side. Everything that Palpatine did led up to the moment when he would ultimately reveal himself as a Sith Lord to Anakin. In the middle of Revenge of the Sith, Palpatine lays his cards out on the table and prays that the years of lies and deception that he sowed into Anakin will bear fruit. Anakin is understandably distraught that his friend and mentor is truly the greatest enemy of the Jedi, and ignites his lightsaber.
Palpatine Almost Ignited His Own Saber To Duel Anakin In ROTS
At the moment that Anakin ignites his saber against him, Palpatine’s hand twitches violently for about two seconds, before he retracts it back into his sleeve. Only later is it revealed during Palpatine’s duel with Mace Windu that he is accustomed to keeping his saber hidden in his sleeve, which sheds new light on his hand twitching with Anakin. When Anakin pulls his lightsaber on Palpatine, it’s as if Palpatine considers igniting his own lightsaber to defend himself. Had he done so, Anakin would most certainly have dueled him rather than reporting him to the Jedi Council.
In any case, Palpatine decides to refrain from making a sudden move against Anakin, and instead leaves the ball in Anakin’s court. Whether his lightsaber was actually in his sleeve at the time is unclear, since he usually kept it hidden in a statue in his office. But his hand clearly indicates that he thought of using it in the heat of the moment against Anakin. Had they ended up dueling, Anakin may have killed Palpatine due to his exceptional abilities—though it's unlikely, given Palpatine’s experience and Anakin’s conflicted emotions. Ultimately, Palpatine made the wisest choice possible by letting Anakin believe he was defenseless.
Palpatine Had Already Won - Anakin Was Merely His Backup Plan
While Palpatine truly wanted Anakin to fall for his lies and join him, having Anakin become his apprentice wasn’t necessary for Palpatine to rule the galaxy. After being elected the Supreme Chancellor in The Phantom Menace, he was already set up to win against the Jedi. As Mace Windu said, Palpatine had control of the Senate and the courts—which meant he essentially had the public in the palm of his hand. Because of his power, Anakin truly believed that the Jedi would attack Palpatine. Nevertheless, Palpatine had the luxury of cutting Anakin out of his master plan if it came to it.
In addition to having the public on his side, Palpatine had Order 66 just waiting to be executed. The Jedi spread throughout the galaxy fighting the Clone War would be killed by the very clones they’d grown to trust—regardless of whether Anakin turned or not. Anakin becoming Darth Vader was the icing on the cake Palpatine had already baked years before. But Palpatine’s true intentions had always been to single-handedly defeat the Jedi and rule the galaxy—in other words, the Revenge of the Sith.