Shatter (Miraculous Ladybug Fanfiction)

When Ladybug is badly injured during a fight, Chat learns her secret identity. He promises to take care of her, and all of Paris, but when a new threat arises, Chat will have to find a way to cleanse the akumas and set everything right himself, even if it's at the cost of his own morality. Semi-Dark/Dark!Chat Noir/Adrien.
Absorbing Akumas is something Chat Noirs had not done for centuries. There had only ever been one Chat to do so, and that was because his Ladybug had died in the line of duty.
Akuma absorption is dangerous, as the negative energy starts turning the person darker and darker, but also more powerful. A tinkling of the bell on Chat's costume sets everything back to normal much like Ladybug's Miraculous Ladybug power, but also tires him out right away. If Chat absorbs too many akumas and continues cleansing by himself, he may not be able to return to his proper civilian form.
To keep Paris safe, though, Adrien will do anything. While Ladybug is out of commission, this is just a risk he will have to take.
Back at school, an injured Marinette starts to see changes in her beloved Adrien, and when an interview with Chat Noir shows that the once silly, pun loving kitty has become serious and dark, Marinette may end up putting two and two together and figure out that they are indeed the same person. She just has to find a way to help him through the rough time, even if she can't walk.