It really is mind-blowing the things people do that are just unfathomable. I have a friend who hosts 2 private suites i her home, ad she's never really had any horror shows with her Airbnb guests, but she also has a separate studio building on her property that she rents out long-term privately. She had rented to a young man and after he moved out, she went in to clean, found the place filthy, and did a thorough top-bottom scrub out.
But it still smelled awful in there, even after leaving the doors open to air out, so she went back in and washed the walls and floor down with strong bleach solution.
Still smelled awful and she couldn't figure out why until she lifted the trap door to the crawl space under the house to find he had just been stuffing all his garbage bags down there for the entire year he lived there.
Now she doesn't live out in the boonies where you have to haul your own trash to the dump- she lives right in town where there is curbside pick-up every week.
She first called a hazardous waste removal company who quoted her $6000 to deal with it. No way she could pay that, so she had to enlist the help of a friend, don a hazmat suit, heavy duty rubber gloves and rubber boots (everything had turned to slime) and go down there herself and pass the trash bags up. At one point, about halfway through, she came up and told her buddy she didn't think she could do it anymore but after a break, and some "You know you have to, you can do it" from her pal, she did resume. When all the bags were out, she had to shovel up the slime into buckets and pour a bag of lime down there. The whole operation took an entire day, a full truckload to the dump, and she couldn't eat anything for an entire day afterwards, she felt so nauseous.
She did get eventually get even with that guy when she found out where he lived about a year later, I can't tell you how, but it was some stellar revenge.
So sorry you are getting such crap guests. @Alex1286