@Bezejouh0
Blocking a guest only stops them booking with you or messaging you in the future. It does not stop them from leaving a review.
However, if you have it in writing on the Airbnb system that they are threatening to leave you a bad review if you do not refund them, then you may have a strong case for getting their review removed, if they post one. That is considered extortion and against Airbnb rules.
However, please be aware that a lot of Airbnb's customer service staff are outsourced, poorly trained and do not understand their own policies. So you take a gamble every time you get them involved!