I had a similar issue recently. There was a leak from a flat upstairs which caused some mould in the bathroom (not too much but definitely was there). It must have happened quickly as the previous host 2 days earlier didn’t notice anything.
Anyway, the guest, who was from the US and who the airport driver had told me behaved “very strangely” in the taxi, reacted by not even contacting me or the onsite receptionist, but by immediately checking out and complaining to Airbnb. Airbnb then cancelled the booking and said I wouldn’t get any money, despite the fact the young lady had already stayed a night. [I mean if it was that big a deal she would have seen in when checking in, it’s a very small flat).
The problem took 30 minutes to repair, but if the guest had reacted in a normal way I would have probably given her a full refund and a good review. I’ve done that on rare occasions before if something out of my control happened. My review score is 4.82 so there are rarely problems.
As it was I emailed airbnb pointing out she had used services (one night stay, “free” airport taxi and cleaning) without paying for them which is against the law, and the value was £90.
Airbnb then paid me the £90 (around 60% of the total booking value) and thanked me for being a good longstanding host.[I wonder if she had to pay that, or if airbnb paid themselves …]
I then left the guest 1 star, “Would not host”, and wrote “no comments” [I can’t really write more as I wasn’t onsite and don’t have a full view of what happened or of the guest herself]. She wrote me a very bad review (I only read the first 4 words in email preview and not the rest, I’ll leave that treat for another time).
Immediately after hers I have two 5* reviews. I’m booked up for 5 months, so hopefully her review will be drowned out by good ones. Although I may write a response if no-one makes bookings for a while.
Also I might ask airbnb to remove her review on the grounds she didn’t follow their procedure, and she is clearly an outlier. But I would guess they wouldn’t agree to that, so perhaps it will just be left there.