I had the same issue with a guest (a little less than a month after I activated my listing) who stayed with me for about two weeks.
Responding to the guest's review is always preferable, and make sure you address all the issues in your response. Silence will not help you, especially when you're just starting out. This reply is also based from a later guest--thankful that I responded as they wanted to see my point of view.
Like @Monica4, I contacted Airbnb, but they did not delete my guest's negative (mixed public) review because of the positive reviews from other hosts. His private feedback to me was very negative.
Many things can happen when you have a long term guest--what appears to be someone who's funny in the beginning may just turn out to be the opposite in the long run.