One common theme is the struggle between Chat Noir's normal self and the akumatized version. There's often a battle within him as he tries to fight the akuma's influence. Another theme is the reaction of Ladybug and other characters. They are usually shocked and have to figure out how to save their friend.
In 'chat noir akumatized fanfic', a very common theme is the exploration of Chat Noir's darker side. Since he's usually a positive and flirty character, seeing him akumatized allows the writers to show a different, more menacing aspect of him. This often ties in with the theme of redemption as well. The other characters, especially Ladybug, strive to bring back the real Chat Noir, and this journey of redemption is a central part of many such fanfics. Additionally, the chaos that his akumatized state brings to Paris is also a frequently explored theme, with the city in disarray and the heroes having to find a way to restore order.
There is a fanfic series that I've heard about where Chat Noir gets akumatized in different scenarios. In one part, his akumatization is caused by Ladybug's accidental rejection. This fanfic shows how his personality twists and how he uses his new powers in a more menacing way. It also has great character development for the other characters as they try to deal with this new, dangerous Chat Noir.
One common theme is the idea of false accusations. In many of these fanfics, Chat Noir is wrongly accused of criminal acts, which leads to a lot of drama and his struggle to prove his innocence.
I'm not entirely sure as I haven't specifically studied 'chat noir sensitive fanfic', but it could potentially include themes like Chat Noir's internal struggles, his relationships with other characters in a more complex and emotional way, or perhaps how he copes with difficult situations in the Miraculous universe.
One common theme is heroism. Chat Noir and his patrol are usually depicted as heroes fighting against evil. Another theme is friendship, as they rely on each other in their missions.
Another theme might be rescue or recovery. The fic could focus on how Chat Noir's friends or Ladybug in particular try to help him when he's in this state. It could also touch on themes of sacrifice, as perhaps he got in this state because of protecting someone. For example, he might have taken a powerful hit from an akuma to save Ladybug, and now he's lying limp, and the story delves into how she deals with that and tries to revive or heal him.
Friendship is also a big theme. Through these fics, their friendship deepens as Chat Noir comforts Marinette. It shows how they can rely on each other even outside of their superhero and civilian identities.
One common theme could be courage. Chat Noir constantly shows courage in battles. Another could be friendship, as his relationship with Ladybug is a big part of his hero journey. And love, not just romantic love, but love for the city and its people.
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.
Identity is a common theme. Chat Noir has to keep his identity a secret, and this can lead to a lot of deep thoughts about who he really is. He may question if he's more of his civilian self or his superhero self. Another theme is love, especially his love for Ladybug. It often consumes his thoughts and makes him wonder about the future of their relationship.
One common theme is the adjustment to married life. They have to deal with living together, sharing responsibilities, and learning more about each other on a deeper level.