In some fanfiction, their relationship might develop due to shared goals. Let's say they both want to stop a new superweapon being developed by the Empire. Working together towards this common objective forces them to interact more, and they begin to see each other in a new light. Vader might show moments of vulnerability, which Leia starts to pick up on, and she realizes there is more to him than just the menacing Sith Lord. This mutual discovery helps in building a more nuanced relationship between them.
There are also fanfictions where the Force plays a big role in their relationship development. The Force might connect them in unexpected ways, like through shared dreams or visions. These experiences can make them more empathetic towards each other. Leia, being strong in the Force herself, might be able to sense Vader's internal conflict, and Vader might be drawn to Leia's purity of spirit. This can lead to a relationship that is full of tension, but also has elements of hope and redemption.
In an alternate universe, Darth Vader could be exiled from the Empire after a disagreement with the Emperor. He then stumbles upon Leia on a remote planet. At first, they are enemies, but as they are forced to survive together against various threats on the planet, they start to understand each other. Leia realizes that Vader is not all bad, and Vader sees in Leia a determination that he once had. This understanding could lead to a slow transformation of their relationship from hostility to friendship, and eventually, they could work together to try and bring about a new order in the galaxy, one that is not dominated by the Empire or the Rebellion but a more balanced one.
In some fanfictions, their relationship is very antagonistic. Darth Vader sees Ahsoka as a reminder of his failed Jedi past and wants to destroy her. Ahsoka, on the other hand, is determined to stop Vader's evil deeds.
In some fanfiction, their relationship starts with pure enmity. Jabba sees Leia as a trophy and a means to gain power over the Rebellion. But as the story progresses, Leia might start to understand Jabba's motives more deeply, and Jabba might begin to respect Leia's tenacity.
In fanfiction, the relationship between Darth Vader and Padme is often a complex and tragic one. Many writers explore how Anakin's fall to the dark side affected their relationship. Some fanfictions might depict Padme's attempts to save Anakin from the dark side, while others may show how their love was doomed from the start due to the political situation in the Star Wars universe.
In many fanfictions, their relationship develops in a complex way. At first, it's mainly about the enmity. But as the story progresses, there could be moments of understanding. For example, Vader might see some of his old self in Ahsoka. Ahsoka, on the other hand, might start to pity the broken man that Anakin has become. This could lead to a strange sort of respect between them, even though they are on opposite sides.
In fanfiction, their relationship could develop more quickly towards mutual understanding. Maybe Luke could convince Vader to turn away from the dark side much earlier, and they could start training together as Jedi. This would be a huge shift from the original story.
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.
Their relationship could start off as adversarial. Darth Vader sees R2D2 as just another piece of Rebel technology to be destroyed. But as the story progresses, he might start to respect R2D2's tenacity and the fact that it has survived so many battles. For example, if R2D2 helps Vader in some small way, like leading him out of a dangerous situation, Vader might start to view the droid differently.
Another way to develop their relationship is through a shared secret. Maybe they both know something about the Force that the rest of the galaxy doesn't. This secret brings them together in a way that defies their initial roles as Rebel and Sith. They have to communicate and collaborate to keep this secret, and in the process, their relationship evolves from pure hatred to something more nuanced, like a begrudging alliance with a hint of mutual curiosity.
In some fanfictions, their relationship develops through a series of battles. Each encounter makes them more aware of the other's strength and weaknesses. For example, Vader might initially see Ahsoka as a mere nuisance but as they fight more, he starts to respect her skills, which in turn makes him question his own choices more deeply. And Ahsoka, she begins to understand the depth of Vader's fall and feels a sense of sorrow for him.