Darth Vader's sad story begins with his fall to the dark side. Anakin Skywalker, who later became Darth Vader, was a promising Jedi. But his fear of losing his loved ones, especially his mother's death and his premonitions about Padmé, led him to be manipulated by Palpatine. He turned against the Jedi Order, participated in the massacre of the younglings. His suit, which kept him alive, was also a symbol of his imprisonment in a way. He lost his identity as Anakin, his connection to the light side, and was left in a state of constant inner turmoil and regret until he finally redeemed himself by saving Luke.
Well, first off, his initial identity as Anakin and his bright future as a Jedi is an important part. Then, the events that led to his downfall, such as the loss of his mother and his love for Padmé. His turn to the dark side was a major element, along with the heinous acts he committed as Darth Vader. His relationship with his son Luke, which was a mix of enmity and the glimmer of hope for his redemption. And not to forget, his final act of self - sacrifice which redeemed him but also showed the depth of his sad journey.
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.