In some fanfictions, 'dark side Luke' might be paired with Palpatine. Palpatine, as a master manipulator, could have a role in Luke's fall to the dark side, and their partnership would be full of political intrigue and dark Force - related activities. Palpatine could use Luke as a tool to further his own evil plans, while Luke might be seeking more power from Palpatine.
Princess Peach is often paired with Dark Mario in fanfiction. Their relationship can be very different from the normal one. Instead of being the damsel in distress, Peach might be a more complex character, perhaps even having a dark side herself and being in a sort of power struggle with Dark Mario. Another character is Luigi. He could be either trying to save his brother from the darkness or be in direct conflict with Dark Mario as he tries to protect the Mushroom Kingdom.
Pepper Potts is often paired with Dark Tony in fanfiction. Their relationship can take on a whole new dynamic as Pepper tries to deal with this darker version of Tony. Another character could be Rhodey. He might be in the story trying to bring his friend back from the dark side. And sometimes, even villains like Loki could be paired with Dark Tony in some really out - there fanfictions.
Vlad Masters is often paired with Dark Danny. Since they both have a connection to Danny's ghostly side, they can have some really intense interactions. It could be a power struggle between them or an alliance of sorts.
Gwen is often paired with Dark Ben in fanfiction. Their dynamic can be really interesting as she tries to bring out the good in him or stop his evil plans. Another character is Kevin. He might team up with Dark Ben for a while, either because they have a common enemy or Kevin thinks he can control Dark Ben's actions.
Naruto can also be paired with Dark Kakashi. Naruto's unwavering belief in the good of people could contrast sharply with Kakashi's darker self. It might lead to situations where Naruto tries to bring back the old, more positive Kakashi, and through their interactions, both characters grow and learn more about themselves.
Mikasa is often paired with Dark Eren. Given their long - standing relationship in the original series, it's natural for fanfiction to explore how she reacts to his darker side. She might try to bring him back to the light or be conflicted about her feelings for him.
Obviously, Rey is the central character as the story is about her fall to the dark side. Kylo Ren might also be a key figure. He could be either a catalyst for her fall, perhaps by tempting her with the power of the dark side, or he could be someone who tries to bring her back later on. Finn and Poe are also likely to be involved. They would probably be the ones trying to save Rey from the clutches of the dark side.
The Emperor or some other powerful Sith lords would likely be involved. They would see Luke as a great prize to turn to the dark side and would use all their cunning and power to manipulate him. Yoda's spirit could also be present, trying to guide Luke from beyond the grave but perhaps being unable to prevent his fall. Han Solo might also play a role, either trying to rescue Luke or being a victim of Luke's new dark side - influenced actions.
Often, a young and brave hero might be paired with Lady Black. This hero could be someone who is still learning about their powers and looks up to Lady Black for guidance.
In some Black Queen fanfiction, the Prince of Shadows is frequently paired with her. Their relationship can be complex, perhaps they are rivals at first but then find common ground. There's also the Enchantress. Since both are female characters with great power, their interactions can range from intense competition to unexpected alliances. And don't forget the Lone Wanderer, who might be drawn into the Black Queen's orbit and become an important part of her story.