One possible plot could be that Jagged Stone discovers the true identities of Ladybug and Cat Noir. Maybe he gets involved in one of their battles accidentally and then becomes determined to help them keep their secret identities safe while also using his fame to distract Hawkmoth.
Another option is to check out Miraculous Ladybug fan communities on social media platforms like Tumblr or Reddit. Fans often share their fanfictions there, or at least can point you in the right direction to find some good Jagged Stone - related fanfictions.
It could be a new villain created specifically for the fanfiction. Maybe an ancient sorcerer who was trapped for centuries and now wants revenge on the modern - day heroes. He has the power to turn things to stone and sees Ladybug as the main threat to his plans.
One possible plot could be that an evil villain discovers a new power that can turn Ladybug into stone. Ladybug is caught off - guard during a battle and gets turned. Chat Noir then has to find a way to reverse the spell. He might search for a magical artifact or seek help from other Miraculous holders.
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.
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.