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.
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.
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 interesting plotline could be a battle that takes place in an alternate universe where Anakin and Obi - Wan have different allegiances from the start. Maybe Anakin is a Sith Lord right from the beginning and Obi - Wan has to face his former apprentice in a more cut - throat battle.
Anakin and Obi - Wan could fit into a Marvel fanfic if they were part of a multiverse - spanning story. The Marvel universe already has concepts like the multiverse. They could be brought in as representatives of a different kind of power (the Force). Anakin's emotional and sometimes unpredictable nature could create interesting dynamics with the more stable Marvel heroes. Obi - Wan could act as a mediator between the two universes, using his knowledge of the Force and his diplomatic abilities to navigate the complex relationships in the Marvel world.
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, Anakin is often very well - written. His internal conflict between the light and dark side can be explored in great detail. His complex relationship with Obi - Wan, from being a beloved apprentice to a bitter enemy, gives a lot of room for character development. Writers can show his journey from a hopeful Jedi to a conflicted individual on the verge of falling to the dark side.
Well, it could be really chaotic. Maybe Anakin and Obi - Wan would be mistaken for new superhumans in the Marvel universe. Their lightsabers would be seen as some sort of high - tech weapons. They might end up getting involved in the Avengers' battles, either as allies or foes depending on how the story is written. Anakin's power could be compared to that of Scarlet Witch, and Obi - Wan's wisdom might be on par with Doctor Strange's.