Maybe a new character from another country comes to Paris. This character has a Miraculous that has powers related to nature. Their role would be to bring a new element to the team. They could use their powers to heal the damaged parts of Paris that were affected by Hawkmoth's attacks, and also help in battles by using nature - based defenses like thick vines to trap villains.
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.
Well, I've read a fanfiction where Ladybug got the power of elemental control. She could use fire, water, earth, and air to her advantage. For example, she could use water to put out fires caused by akumas or use air to create a shield. It made the battles more exciting and unpredictable. And in another one, she had the power of telepathy which helped her understand the akumas' motives better and communicate with her allies more effectively.
There could be a fashion designer from a rival school who is jealous of Marinette's swimwear designs. This character could be a bit of a troublemaker and might unknowingly help Hawkmoth in his plans to steal Marinette's designs. But in the end, she could see the error of her ways and become a friend.
A new villain could be a former Miraculous holder who turned evil due to some misfortune. Maybe they felt betrayed by the Order of the Miraculous and now seek revenge. Another possibility is an alien entity that is attracted to the power of the Miraculouses and wants to use them to conquer Earth.
In this 'Miraculous Ladybug Criminal Ladybug Fanfiction', there could be a lot of potential storylines. One possibility is that an external force is influencing Ladybug to commit crimes. It could be a new villain who has found a way to manipulate the Miraculous. This would create a great conflict as Ladybug has always been the symbol of good. Her friends and allies would be in shock and would have to find a way to stop her without hurting her. The story could also explore her internal struggle, as she might be aware of what she's doing but unable to stop herself.
A new villain could have a weapon that specifically targets Ladybug's powers. When she tries to use her yo - yo or her powers of creation, it backfires and causes her harm. This would force her to rely on her wits and Chat Noir more than ever. They would need to find a way to neutralize the weapon and heal Ladybug.
In a fanfiction, Ladybug could get hurt as a result of a trap set by Hawkmoth. He might have studied her fighting patterns and set up a situation where she is lured into a place full of obstacles that cause her physical harm. This would not only test her physical strength but also her mental resilience as she tries to figure out how to escape and continue her fight against evil.