I made this 5 seconds ago.
There's a cleaning-themed villain named SpringCleaner washing the city by flooding people's houses with soap water. If anyone litters or dissuades cleaning, she turns them into Dark Janitors. Mainly her powers include flood-washing houses, control of water and soap, mop combat, flying on a broomstick. Akumatized object is Janitor's closet keys. Ladybug and Chat Noir obviously defeats and de-evillizes her, then we cut to Hawkmoth in his lair, fuming over his defeat.
Ladybug and Chat Noir: Pound it!
Hawkmoth: You may have escaped me this time, Ladybug. But I promise you! Paris shall be SPOTLESS when I'm done with you!