A possible plot is that Adrien is akumatized after his father is extremely harsh on him for not following the family's strict rules. His akuma form, 'Rebel Son', might have a look that combines his Chat Noir features with a more rebellious and angry look. Marinette could be akumatized when she's framed for something she didn't do at school. Her akuma form, 'Innocent Victim', would have a look of someone who has been wronged and is out for revenge.
Well, a plot could revolve around Adrien being akumatized when he discovers a dark secret about his mother. This could lead to his akumatized form having powers related to uncovering hidden truths and punishing those who have been lying. Or perhaps he's akumatized because he's tired of being in the shadow of Chat Noir. His akumatized self then tries to prove that Adrien is just as important as his superhero alter - ego. Also, he could be akumatized due to a betrayal from a friend, and his akumatized form focuses on isolating that friend from everyone else.
Well, perhaps in the fanfiction, Marinette is akumatized due to the pressure of keeping her identity a secret. She might start to feel isolated and that no one really understands her. Her akumatized form could have powers related to secrecy and shadows. She could create illusions to deceive those around her, especially Ladybug's enemies who are trying to find out her true identity. And she might also use her powers to manipulate the memories of those who get too close to the truth.
Maybe their child gets sent back in time to when Adrien and Marinette were still just friends and classmates. The child then has to figure out a way to get back to their own time without changing the past too much. They might accidentally cause some comical misunderstandings between their parents - to - be in the process.
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.
In some 'Adrien gets akumatized fanfiction', his akumatization could be caused by a misunderstanding with his father. This could lead to his akumatized form having powers related to control or isolation, like being able to trap people in a sort of prison made of his negative emotions. The story could then focus on how Marinette, as Ladybug, tries to reach out to the real Adrien inside the akumatized form. She might have to dig deep into their relationship and use memories they've shared to break through to him.
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 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.
One idea could be that they face challenges in their superhero lives while being pregnant. For example, they have to keep their identities secret even more carefully to protect their unborn child. Another could be that they discover new powers related to the pregnancy, like a connection between the baby and the Miraculous.
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.
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.