Maybe some of the Jedi Council members. They were the ones who were constantly in conflict with Palpatine's plans, so they could be in the story to show the power struggle between the Jedi and Palpatine.
Anakin might betray Palpatine to save someone he loves. If Palpatine threatened Padmé in some way, Anakin would surely turn against him. After all, Anakin's love for Padmé is one of his strongest driving forces.
In a fanfiction where Naruto is hired by Palpatine, one possible scenario is that Naruto's sense of justice clashes directly with Palpatine's tyranny. Naruto, being used to a world where there are clear good and bad guys, would quickly realize that Palpatine is on the wrong side. He might try to persuade Palpatine to change his ways, using his own experiences of redemption and growth. However, Palpatine is a very stubborn and power - hungry character. So, it would likely result in a battle of wills. And depending on how the fanfiction is written, Naruto could either succeed in changing Palpatine or have to fight against him to protect the innocent in the Star Wars universe.
One possible plot could be that Anakin discovers Palpatine's plan to destroy the remaining Jedi earlier than in the original story. This early discovery gives him the chance to turn against Palpatine and kill him to save the Jedi order. Maybe he finds some hidden evidence that convinces him once and for all of Palpatine's true intentions.
The story could also center around Palpatine's relationship with other key characters in the Star Wars saga. For instance, his interactions with the Jedi before he fully revealed his true nature. It could show how he managed to deceive them for so long, his schemes to undermine the Jedi Order from within. It could also touch on his influence on Anakin Skywalker's fall, exploring the details of how he lured Anakin to the dark side step by step.
It could be that a powerful wizard in the Harry Potter universe sends Harry to defeat Palpatine for some greater good. Harry's quick thinking and his array of spells like Expelliarmus or the Killing Curse (although he hates to use it) could potentially be used against Palpatine. Since Palpatine is used to dealing with lightsabers and the Force, Harry's magic could catch him off - guard.
One idea could be that Palpatine somehow discovers the wizarding world of Harry Potter. Maybe he sees it as a new realm to conquer. He could try to manipulate the Ministry of Magic using his Sith mind - tricks, and Harry Potter would have to figure out who this strange new threat is and stop him. It would be a clash of two very different kinds of magic.
The plot might involve Anakin being influenced by the good side of the Force more strongly. He starts having visions of a dark future if Palpatine continues to rule. Anakin then starts to secretly gather allies, including some Jedi who have survived Order 66. Together, they plan an attack on Palpatine. Anakin, with his enhanced power, confronts Palpatine directly. Their battle could be not just physical but also a battle of wills, with Anakin finally emerging victorious as he overcomes the dark side's allure within himself.
Well, Palpatine's background is filled with secrecy and deception. He was a master of political manipulation and used his Sith powers in the shadows to gain control. His early life was marked by his apprenticeship under Darth Plagueis and his plotting to overthrow the Republic.