She could join the dark side if she was manipulated. There might be a powerful and cunning character who preys on her insecurities and convinces her that the dark side is the right path. For example, they could make her believe that the Leaf Village's values are false and that the dark side has a more 'true' way of doing things. Maybe she was also influenced by seeing the dark side's seeming freedom from the strict rules of the village.
She would become more cynical. Instead of her usual optimistic self, she would start to see the world in a more negative light. Her trust in others would be severely damaged. For example, she might not believe in the goodness of her friends anymore.
In fanfiction scenarios where Naruto turns to the dark side, it could start with a personal tragedy. For example, if Hinata was killed by someone from the Leaf Village under false accusations. This could shatter Naruto's belief in the village and its values. He would then be vulnerable to the influence of the dark side. Once on the dark side, he could use his charisma to recruit others who have also felt wronged by the ninja world. He might form his own group, with different rules and goals from the traditional ninja villages. His journey to the dark side would not only change him but also send shockwaves through the entire ninja world, as he was once seen as a symbol of hope and a force for good.
In fanfiction, Anakin joining the Dark Side often has complex motives. It could be due to his fear of losing Padmé. The Dark Side might seem to offer him a way to save her, so he succumbs to its power.
One possibility could be that Batman's sense of justice becomes warped. He might start using more extreme and unethical methods to 'clean up' Gotham. For example, he could be more brutal with criminals, foregoing his usual no - kill rule. His relationships with his allies would also be severely strained. Alfred would be deeply disappointed and the Bat - family might split apart as they try to oppose his new, darker path.
Well, perhaps Harry gets tired of being constantly in danger and feeling unappreciated in the wizarding world. He might be lured by the Dark Side with promises of power and safety. Voldemort could offer him a place by his side, showing him a different view of magic that seems more appealing in a warped way.
In this fanfiction, it could be that Rey has some personal losses that make her turn. She might lose someone dear to her and in her grief and anger, she decides that the dark side can give her the strength to prevent such losses in the future. She then starts learning the ways of the dark side, which changes her relationships with her friends.
Another plot is Anakin's search for greater power in fanfiction. He believes that the Jedi Order is holding him back from reaching his full potential, and the Dark Side seems to offer unlimited power. So he makes the fateful decision to join it. This often involves his internal struggle between the light and the dark within him, which is a great source of drama in these fanfictions.
One possibility is that Adrien feels betrayed by his friends or the heroes around him. Maybe he discovers some dark secrets about the so - called good side that make him question his loyalty. For example, if he finds out that the heroes have been using him or hiding important information from him. This could push him towards the dark side where he might think he can find more truth and power.
If Luke joins the Dark Side, it would completely change the dynamic of the Star Wars universe. His friends would be shocked and heartbroken. Leia, for instance, would probably try to bring him back. The Rebellion would lose a great hope and the Empire might gain an unexpected and powerful ally. It could also lead to a different kind of struggle within the galaxy as those who once believed in Luke now have to face him as an enemy.