Guests, like fish, go bad after 3 days.
When you leave and your guest stays behind, YOU are responsible for whatever they do or don't do. So, it's up to you to give proper notice (which I imagine you haven't done) and then evict through the courts.
If you don't, the landlord is left with having to do it and incurs the legal expense and loss of rents and is guaranteed to be coming after you for the money which, by the time it's done, could be several thousands of dollars and result in a lawsuit against you which you will lose and the judgment will end up on your credit report.
If you want to avoid all that I suggest you offer your guest "cash for keys." In other words, offer him money to leave but don't pay him until he and all his stuff are out the door and you get the keys and a written agreement.

