Luke Skywalker could be another key character. Since he is Vader's son, his presence could add an interesting dynamic. He might be the one who somehow triggers the battle between Anakin and Vader, or he could be in a position to influence the outcome of their fight, perhaps by appealing to the remaining good in Anakin or by facing off against Vader himself in a three - way struggle.
It really depends on how you write it. If it's Anakin at his peak before turning to the dark side, he has a lot of raw power and potential. But Vader has years of experience as a Sith Lord. So, it could go either way.
Darth Vader could encounter advanced droids that have developed personalities and even some form of Force - like abilities in this future. These droids might be a new challenge for him as they are not like the droids he is used to dealing with in his own time. He may also meet future versions of his former allies or enemies, who have been reincarnated or cloned in some strange new way, with different personalities but still with a connection to their past selves.
In the 'naruto is like darth vader fanfiction', their journey of self - discovery could be seen as similar. Naruto has to constantly figure out his place in the ninja world and how to control his power. Darth Vader is on a journey of self - discovery too, as he grapples with his identity as Anakin Skywalker and his role as Darth Vader. They also have a sense of isolation in some ways. Naruto often feels alone in his struggles, and Darth Vader is isolated in his dark armor, cut off from his former self and many human connections.
One idea could be a what - if scenario where Anakin in his pre - Vader state somehow gets a glimpse of his future as Vader. He could then fight against the dark side within himself that would turn him into Vader. Another could be a time - travel plot where Vader is sent back to face Anakin, and Anakin has to decide whether to accept his possible future or fight against it.
A fan fiction could also explore a parallel universe where Anakin and Darth Vader are two separate entities that co - exist. They are forced to fight not because of Anakin's fall, but due to some external force that wants to see the two most powerful Sith - like beings battle it out. This could lead to an exploration of their different fighting styles and the power dynamics between them.
Well, it's likely that there are bounty hunters. Since Vader often has need of their skills for certain tasks. They would be characters who are in it for the money but also fear Vader. And then there are the stormtroopers. They are a constant presence, following Vader's commands and being part of his military operations.
Darth Vader could emerge victorious. His mastery of the Force gives him an array of abilities such as telekinesis and mind control. He could potentially use these to disable Naruto before he has a chance to launch a major attack. Also, Vader's lightsaber skills are top - notch. If he can get close to Naruto, he could deliver a fatal blow. And in a one - on - one situation, without the help of his friends, Naruto might find it difficult to counter Vader's unique powers.
In fanfiction, we can also see how an OC might change the power balance between Vader and Sidious. If the OC is a powerful ally to Vader, it could lead to a split in the Sith order. Or if the OC is a double - agent working for both, it can create a complex web of lies and deceptions that make for a very engaging read.