Thank you for explaining the problem. One option would be deleting the user, but I assume you would like to keep old posts.
The second option would be to anonymize the user. That would prevent them from logging in again, and you will keep all conversations (under an anonymized username).
However, if you would like to keep their original username, we would need to develop a new button called “disapprove.” We would place it here:
If a “disapproved” user tries to log in, they would see this screen:
Would the anonymize feature work for you? It might take us a moment to develop that “disapprove” feature.