One interesting Vader redemption fanfiction could be one where Vader has a series of dreams about his past self as Anakin. These dreams gradually make him question his loyalty to the Dark Side. He starts to secretly help the Rebellion in small ways, like warning them of minor Imperial attacks.
There could be a fanfiction where Vader has an unexpected alliance with a rebel. Maybe they are forced to work together to stop a greater threat, like a rogue Sith or a powerful alien race that wants to destroy both the Empire and the Rebellion. This would put Vader in a complex situation as he has to deal with his loyalty to the Emperor and his newfound, albeit temporary, partnership with the rebel.
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.
Typically, Vader's redemption starts with a moment of self - reflection. Maybe he witnesses an act of extreme cruelty by the Empire that makes him question his place. Then he begins to reach out to the Light Side, often through small acts of kindness or defiance against the Emperor.
Well, it depends on your taste. However, 'The Early Redemption of Anakin' is quite popular. It delves deep into what could have happened if Anakin had been redeemed before his full - fledged turn to Darth Vader. Then there's 'Star Wars: Early Redemption Arc' which is a collection of short stories all centered around the concept of early redemption. There are also some lesser - known but very well - written ones on independent fanfiction blogs that are worth exploring if you're into this theme.
A redeemed bounty hunter could be an interesting concept. They take on a job that turns out to be for an evil cause. Feeling guilty, they turn against the employer and start working towards redemption by helping those the employer had targeted, all while dodging other bounty hunters who still follow the code of the hunt.
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.
Another story is about Vader's relationship with his son, Luke Skywalker. Vader was initially set on turning Luke to the dark side. But in the end, his love for his son redeemed him. There were many encounters between them, like the one on Cloud City, where Vader revealed to Luke that he was his father, which was a huge shock in the Star Wars saga.
A cool concept would be a crossover with the Star Trek universe. Darth Vader's Sith ideology would clash with the Federation's principles. He might be intrigued by the advanced technology of the Star Trek world, and there could be an epic battle between the power of the Force and the technology of the future. Or perhaps he'd form an unlikely alliance with some of the more morally ambiguous characters in Star Trek.
In some fanfiction, there could be a scenario where Leia discovers her connection to Darth Vader much earlier. Maybe she has a vision or some sort of Force - related encounter that reveals the truth. This would lead to a very different dynamic in the story as she grapples with this knowledge and how it affects her fight against the Empire. For example, she might try to reach out to the good in him, creating an internal struggle for Vader between his loyalty to the Emperor and his newfound connection to his daughter.
One interesting story could be about Darth Vader secretly having a change of heart during the events of Star Wars Rebels. Maybe he has a brief encounter with a Rebel that makes him question his loyalty to the Empire.