In some fanfictions, Darth Vader's redemption is linked to his relationship with his daughter, Leia. Maybe he discovers her identity before the events in 'Return of the Jedi' and starts to change his ways in order to protect her and make amends for his past actions. He could start to undermine the Empire from within to ensure her safety.
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.
Time travel could offer Darth Vader a chance to relive key moments and make different choices. For example, he could go back to the moment before his fall to the dark side and resist Palpatine's temptations. This would completely change the course of the Star Wars saga. Maybe he would see the error of his ways earlier and not cause so much destruction.
In a lot of fanfiction, a connection to his past self, Anakin Skywalker, is re - established. This could be through a memory triggered by an event or a person. For instance, if he comes across a Padawan in the Empire who reminds him of his own days as a Jedi. Once that connection is made, he begins to fight against the dark side within him and seek redemption. It's a long and difficult process as he has to overcome years of indoctrination into the dark side.
Darth Vader could meet advanced droids that have personalities and abilities far beyond what he's used to. These droids might see him as a relic from a bygone era. He could also meet future scientists who are intrigued by his cybernetic enhancements and try to study him. Additionally, there's a chance he meets descendants of his former allies or enemies, which would create a complex web of relationships and interactions.
Padmé could be a main character. Since Darth Vader is without his suit, it could be a scenario where he's reliving memories of her, and she could appear as a Force ghost or in his dreams, guiding him in some way. Another character could be Obi - Wan Kenobi. Their relationship was complex, and without the suit, Vader might be more vulnerable, and Obi - Wan could try to sway him back to the light side.
He might be shocked by the advanced technology. The Empire's weaponry would seem primitive compared to future tech. He could also be intrigued by the new forms of the Force if they had evolved.
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.