A fanfiction writer can start by really understanding Marinette's character. Know her strengths, weaknesses, and what makes her tick. Then, think about what could push her over the edge to get akumatized. It could be something like a major betrayal or repeated failures. When writing the akumatized form, they can give her powers that are related to her negative emotions but still in line with the Miraculous universe's rules.
If Adrien and Marinette were akumatized, their relationship would become very strained. As akumatized individuals, they would be full of negative emotions which could cloud their judgment. Adrien, who usually has a soft spot for Marinette, might not recognize her in his akumatized state and could even attack her. Marinette, too, would be in a different mental state and might see Adrien as an enemy, forgetting their previous friendship and any budding romantic feelings.
Well, obviously Marinette herself is a central character. Chat Noir is also very common as he usually has to deal with akumatized Marinette. Alya is often there too, as Marinette's friend. She might try to help Chat Noir understand what's going on with Marinette or try to find a way to reach out to her.
One interesting plot could be Marinette being akumatized into a form that has the power to reverse the roles of heroes and villains in Paris. So, the akuma victims become the ones trying to save Ladybug and Chat Noir. Another plot might involve her akumatized form having the ability to create illusions of everyone's worst fears, which leads to chaos in the city as people are forced to face their phobias.
Hawkmoth is usually the main antagonist. Since he is the one who akumatizes Marinette in the first place. He takes advantage of her negative emotions, like her insecurities or anger, to turn her into an akuma and use her for his own evil plans.
One interesting aspect could be the character transformation. Seeing Marinette, who is usually kind - hearted, turn into an akumatized form offers a fresh take on her personality. It can explore darker emotions and motives that she doesn't typically display.
In a fanfiction, Marinette's akumatized form might incorporate elements from her negative emotions. If she's akumatized due to jealousy, her form could have green accents symbolizing envy. Her eyes could be a glowing red, and she could have wings made of thorns, representing how her once - gentle nature has become prickly. She might also carry a scepter that can spread negative thoughts among people she targets.
In a fanfiction scenario where Marinette gets akumatized, it's a really fascinating concept. Marinette is known for her strong will and positive attitude, but if she's akumatized, all that could be flipped. Her akumatized form might be influenced by her repressed emotions, such as her jealousy over Lila's lies being believed so easily. Her akuma - powered actions could start to cause chaos in Paris. And it would be a great opportunity for the other characters to step up and try to save her, not just as Ladybug, but as Marinette. There could be a lot of self - discovery and character growth for everyone involved as they face this new and unexpected threat.
One possible plot could be Marinette getting akumatized because she feels constantly overshadowed by Ladybug's responsibilities. She might turn into an akuma with powers that are a twisted version of her creativity, like creating chaotic and unmanageable 'designs' that cause havoc in Paris.
There could also be antagonists like Hawk Moth. Since he is the one sending the akumas, he would be involved in the backstory of Marinette's akumatization. He might have a particular reason for targeting Marinette this time, which could be explored in the fanfic. And perhaps some new characters could be introduced as a result of Marinette's akumatized state, like other heroes or villains that are drawn to the chaos she creates.