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.
Anakin is likely to win. He has the power of the Force on his side. He can anticipate Clovis's moves, dodge attacks, and launch powerful counter - attacks. Clovis doesn't have any supernatural abilities like Anakin. Even if Clovis tries to use his wealth or political connections against Anakin, Anakin can use the Force to find a way around those obstacles. His training as a Jedi gives him the discipline and combat expertise that Clovis lacks.
In some fanfics, there might be a plotline where Palpatine tries to corrupt Anakin even further during the battle, using psychological warfare. Anakin, on the other hand, has to resist this while also fighting for his life. This adds a layer of psychological drama to the physical fight between them.
One interesting plot point could be the power struggle between Anakin and Clovis. Anakin is a powerful Jedi, while Clovis is often involved in political and economic affairs. Their clash might involve different ideologies, with Anakin representing the Jedi way and Clovis perhaps having more self - serving motives. Another aspect could be a love triangle situation if there is a female character involved who has connections to both of them, which would add a lot of drama and tension to the story.
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.
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.
It really depends on how the author writes it. If the fanfic focuses on Anakin's potential and his growth beyond what we saw in the movies, he could win. For example, if he has fully mastered some new form of lightsaber combat or Force ability.
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.
Anakin could be angry. He might see his other self as a threat, especially if one represents his dark side and the other his light side. There could be a power struggle between the two versions of himself as they try to assert dominance over the other. Or he could be curious and eager to learn from his other self, about what he could have been or what he can still become.
Anakin could encounter future versions of his friends or enemies from the past. For instance, he could run into a future version of Obi - Wan Kenobi who has also somehow traveled to that future time. Or perhaps he meets a new generation of Sith who have different motives and methods compared to the Sith he knew in his own time. They could challenge his understanding of the dark side and the Force in general.