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.
In many fanfictions, Obi - Wan might use his deep knowledge of the Force. He could reach out to Anakin through a Force - bond, calming his inner turmoil and guiding him away from the dark side. For example, he might remind Anakin of their past together, their training, and the values they once held dear.
Maybe the Force itself could be an antagonist in a sense. The light side of the Force would be trying to pull Obi - Wan back from the dark side. And the natural balance of the Force that doesn't want too much dark side influence could be working against Anakin's plan to turn Obi - Wan. So the Force, in its own way, could be the main antagonist.
One idea could be a story that focuses on Anakin's internal struggle between his love for Padme and his fall to the dark side as Darth Vader, while Luke and Leia unknowingly grow up in the shadow of their father's actions. It could explore how their lives might have been different if Anakin had not turned, and how they eventually come to terms with his true identity.
In such a fanfiction, one possibility is that Anakin Skywalker might initially be in shock upon seeing Darth Vader. He could struggle to come to terms with what he has become. Maybe there would be a battle of wills as Anakin tries to fight against the dark side within Vader.
In the fanfiction where Darth Vader travels back in time, his bond with Obi - Wan Kenobi would be full of possibilities. Imagine Vader going back to a time when he was still Anakin. He might have a newfound respect for Obi - Wan, knowing all that Obi - Wan tried to do for him in the future. Obi - Wan, for his part, could be shocked to see this changed Anakin. They could form an alliance against the emerging threat of the Sith, or Vader could try to get Obi - Wan to understand his view of the Force. Their relationship would no longer be simply that of a Jedi and his fallen apprentice, but something far more nuanced and unpredictable.
Anakin Skywalker's character development is a long and complex journey in 'The Rise of Darth Vader: A Star Wars Story'. In the beginning, he was a young, talented Jedi with a big heart. But his pride also grew as his power increased. He didn't like being told what to do by the Jedi Council. His relationship with Padmé was against the Jedi Code, which added to his internal conflict. As the story progresses, he faced more challenges and temptations. His desperation to save Padmé from a supposed death made him trust Palpatine more. Palpatine exploited Anakin's weaknesses, his love, his pride, and his doubts about the Jedi. This continuous manipulation and Anakin's own internal battles led to his downfall and the rise of Darth Vader.