Mold in the shower.
Provide only one key per room, the key used to turn on the electricty so every time you leave and come back, the room is so hot and humid. It took a while for the AC bring down the temperture.
Offered you an upgrade room with an xxx amount then charged you 3 times more when you checked out. They really know how to scam you!
If you used the plastic spoon in the room to mix your coffee, they will charge you a fee even though it is a disposable one (their excuse is it will be reused for the next guest, so if you throw them away, they will charge you, that is so unsantized) and supposed to be complementary.