Based on the title, it seems the main character could be the 'queen of mean'.
I'm not entirely sure specifically what 'queen of mean miraculous ladybug fanfiction' is about without reading it. It could be a fanfiction that focuses on a 'queen of mean' character within the Miraculous Ladybug universe. Maybe it's about a powerful and perhaps villainous female character who causes trouble for the main characters like Ladybug and Cat Noir.
An akumatized villain could be the main character in a different kind of fanfiction. The villain was once a normal person but due to some heartbreak or injustice, they are akumatized into a dragon - like form. The story could then be about their journey of redemption or how Ladybug and Chat Noir try to bring them back to their normal self.
Maybe one of Ladybug's classmates who is also a cheerleader. For example, Alya could be a cheerleader in this fanfiction. She already has a nose for news and is friends with Ladybug, so she could use her cheerleading skills to get closer to the action and help Ladybug in a different way.
Chat Noir is also very interesting. His flirty and carefree nature could be a contrast to the seriousness of the Prime Queen threat. Maybe he tries to use his charm to distract Prime Queen or to get information out of her. And his loyalty to Ladybug could be explored more deeply during this event.
I think Chloe could be really interesting. Since she was Miracle Queen, exploring her motives and her internal struggle would add depth to the story. Maybe she wasn't fully in control when she became Miracle Queen and there's more to her actions than meets the eye.
Once upon a time in Paris, Queen Bee was having a tough day. She had just had an argument with Ladybug. In the Miraculous Ladybug style, she decided to prove herself on her own. She started patrolling the city alone. As she flew across the rooftops, she noticed a strange akuma - like shadow. Without hesitation, she dived towards it. But it was a tricky illusion created by Hawk Moth. Queen Bee quickly realized her mistake and called for backup. Ladybug and Chat Noir soon arrived, and together they defeated Hawk Moth's new scheme.
Obviously, Ladybug could be the main character. Since it's about cleaning the house, she could be shown in a more domestic side of her life, which is not often explored in the original series.
Ladybug could be the main character. Since she is the main protagonist in the original series, it would make sense for her to be in the center of this fanfiction. She could be the one to witness the car accident, or be directly involved in it somehow, like trying to stop it from happening with her powers.
Obviously, Marinette and Adrien would be key characters. Marinette could be the host of the sleepover, and Adrien might show up unexpectedly, either as himself or as Chat Noir. Their interactions would be the focus, whether it's some cute and awkward moments between them.
Obviously, Ladybug and Cat Noir are the main characters. Their immortality would likely be a central focus of the story. They would be the ones experiencing the changes and challenges that come with living forever.