If you no longer want a user to have access to a particular SQL Server, you must drop the user's login ID from that server. Only the SA can drop a login ID.
You cannot drop the login ID of a user who is the owner of any database or a database object in the current database. You must transfer the ownership of the any database owned by the login ID, and drop owned objects from the current database before dropping the owner's login ID.
The logins for that server are listed.
The login ID is removed.