In some fanfictions, Marinette might be betrayed by Chat Noir. Maybe he falls for an akumatized villain who convinces him that Marinette is not worthy of being Ladybug. So he starts to undermine her in battles or reveals her secrets to the wrong people. It would be a major shift in their relationship as they are supposed to be partners. Also, it could be that her classmates, like Chloe, manage to turn the whole class against Marinette. They might spread lies about her that are so convincing that even her closest friends start to believe them and shun her.
One possible plotline could be that Marinette's best friend reveals her secret identity to someone she shouldn't. This would make Marinette feel extremely betrayed as her identity is crucial in the Miraculous world. Another could be that the people she thought were on her side in the fight against Hawk Moth turn against her due to false accusations. For example, if someone spreads the rumor that Marinette is working with Hawk Moth, her allies might start to doubt her and treat her coldly, which is a huge betrayal.
In many fanfictions, Marinette might get injured during a battle with an akumatized villain. For example, she could be caught off - guard while trying to protect someone. Her injury could then lead to some really emotional moments, like Adrien finding her and being extremely worried. This could also be a turning point in their relationship, making Adrien realize his true feelings for her.
In a Marinette - missing fanfiction, it could be that she has amnesia and has wandered off. She might not remember who she is or where she lives. The other characters would notice her absence quickly. Tikki would be especially worried and try to guide Chat Noir to find Marinette. The city of Paris would seem a little less bright without her, and the story could focus on how everyone comes together to find her and restore her memory.
In some fanfictions, Marinette might be bullied because of her identity as Ladybug. Enemies could target her civilian self to try and break her spirit. For example, Hawk Moth could send out an akuma to a classmate who already has some jealousy towards Marinette. This classmate then starts to bully her, but Marinette uses her wits and the power of friendship to fight back.
A common plotline is Marinette's hair being down as a sign of a transformation in her character. For example, she might let her hair down when she decides to be more assertive or when she's finally coming to terms with her feelings for Adrien. It shows a more vulnerable and yet confident side of her.
One common plotline is about Luka helping Marinette deal with her feelings for Adrien. He becomes her confidant and through that process, they start to develop deeper feelings for each other.
In many fanfictions where Marinette can fly, it often gives her a new level of confidence. For example, she might use her new ability to quickly get to akuma battles and surprise the villains. She could also use flying to have some peaceful moments above Paris, away from the daily chaos. It adds a really interesting dynamic to her character as she already has so many responsibilities as Ladybug.
A possible plot idea is that Marinette is akumatized after being wrongly accused of something at school. Her akumatized form could have the power to manipulate people's memories, making them believe false things about their friends. This would cause a lot of chaos and mistrust in Paris. Chat Noir would have to find a way to reach the real Marinette inside the akumatized shell and convince her to break free. It would be a story full of drama and action.
One possible scenario could be that Marinette gets injured during a fight as Ladybug and is rushed to the hospital. In the fanfiction, her friends might come to visit her, and there could be some sweet moments between her and Adrien as he's worried about her. Maybe she has to keep her identity a secret even while in the hospital, which adds an extra layer of tension.
One possible fanfiction could be about Marinette transforming into a mouse - themed Miraculous holder. Maybe she discovers a new mouse - themed Miraculous in a hidden part of Paris. This could lead to her having new powers like super - speed and the ability to fit into small spaces. She could use these powers to outwit Hawk Moth's akumas in a really unique way, and her relationship with Adrien might also take an interesting turn as she tries to keep her new identity a secret from him.
In Miraculous Ladybug fanfiction, Marinette in a bikini could be part of a beach - themed story. Maybe she's on vacation with her friends. It could be a fun and light - hearted scenario where she shows off her confidence and style while enjoying the sun and sand.