The best thing to do is changing the role of the user you want to disable. If you want to band IP simply login to your CPanel ==> Security ==> Ip Deny manager. All you need to do add the ip and click add and it wont be able to visit your website until you remove the banned.
On more thing if the visitor changing the last digits of his IP
Then band 208.86.198 only and he want be able to come to your website even if he change them.
You can banned as many as you want from your Cpanel.