Ladybug would be extremely shocked and heartbroken. She has always seen Cat Noir as her partner and friend, and to see him akumatized would be like losing a part of herself. She would be determined to save him at all costs, trying to find a way to communicate with him beneath the akuma's influence.
Plagg, Cat Noir's kwami, would be devastated. He would feel responsible in a way, since he is Cat Noir's guide and source of power. Plagg might try to reach out to Cat Noir on his own, using their special bond, and at the same time be looking for ways to help Ladybug in the fight against the akumatized hero.
One possible fanfiction could involve Chat Noir being akumatized after a major argument with Ladybug. Maybe he feels constantly overshadowed or unappreciated. The akuma could enhance his negative feelings, making him more aggressive and less in control. His powers might become distorted, and he could start causing chaos in Paris. Ladybug would then have to find a way to reach out to the real Chat Noir inside the akumatized form and purify the akuma.
In a fanfiction, Alix might get the Bunny Miraculous in a rather unexpected way. For instance, the Miraculous could be sent to her from an alternate future where she is the only hope. Once she has it, she struggles at first to understand the time - jumping abilities. But as she practices, she becomes a crucial asset in the fight against Hawk Moth. She could use the power to go back and prevent some of Hawk Moth's early akumatizations, changing the course of the battle.
Definitely Tikki and Plagg. These Kwamis are essential to the Miraculous universe. Their interactions with Cat Noir and Ladybug, as well as their own little quirks and personalities, can make for really fun fanfiction. Additionally, Sabrina, Chloe's sidekick, can be an interesting character to include. She could have her own story of breaking free from Chloe's control or getting involved in the hero - villain drama in some unexpected way.
She would also be very determined to bring him back to the good side. Ladybug might search for a way to break whatever spell or influence has made Chat Noir evil. She could look for a special power - perhaps from another Miraculous or a magical item - that can reverse the change. And in the meantime, she has to be careful not to get hurt by Chat Noir while still trying to protect Paris.
In an akumatized Ladybug fanfiction, the akuma might enhance her powers in unexpected ways. For example, her Lucky Charm could become a more powerful and unpredictable object. Her akumatized form might also have a darker and more menacing look, perhaps with a more aggressive fighting style. Writers could explore how the heroes and villains interact with this changed Ladybug.
To write a good Miraculous Ladybug Cat Noir fanfiction, you should start with a strong concept. It could be a 'what - if' scenario, like what if Ladybug and Cat Noir's identities were revealed early. Then, build your story around that. Also, pay attention to the relationships between the characters. The friendship and budding romance between Ladybug and Cat Noir are important elements. Don't forget to add some twists and turns to keep the readers interested. Maybe a character they thought was a friend turns out to be working for the villain.
In a fanfiction of this kind, the akumatized reader could be a huge fan of Ladybug, but after being rejected one too many times when trying to offer help or get an autograph, they get akumatized. Their akumatized form might have powers related to disappointment, like creating illusions of the worst - case scenarios for Ladybug and Chat Noir, making their battles more difficult. To defeat this akumatized reader, Ladybug and Chat Noir would need to show the reader that they do value their support.
There's a fanfiction called 'The Miraculous Origins'. It delves deeper into the backstory of the Miraculous. It explores how the Miraculous were created and how they came to be in the hands of the current holders. It's a long read but worth it for fans who want to know more about the lore of the Miraculous Ladybug Cat Noir universe.
Marinette's friends, like Alya, would be heartbroken. Alya, being Ladybug's biggest supporter, would probably feel a sense of loss and confusion. She might start to investigate Ladybug's death, trying to figure out what really happened. The other classmates would also be affected, with the mood at school becoming very somber.
The storyline could progress with Cat Noir initially being excited about having both Miraculouses. He might try to show off his newfound power, but quickly realizes that it's not as easy as he thought to handle both at once.