Comment blacklisting works well, but what if you actually want to stop someone from even reading your blog? This plugin will take care of that for you.
It uses .htaccess file modifications to deny access to your blog from particular IP addresses (Deny from) and then follows up with an ErrorDocument 403 redirect to a URL of your choice. It doesn’t hook into WordPress, which makes it a lot faster due to no database or PHP calls.

WP-BlockYou

A plugin that can be used to block or "ban" users via their IP address from viewing your blog, and then redirecting them to a URL of your ch …

Another Cup of Coffee Limited

FeenBan is a simple WordPress plugin that implements user <a href="http://en.wikipedia.org/wiki/Hellbanning" rel="nofollow ugc">shadowbanning</a> (or hellbanning) for comments.
Comments by shadowbanned users will be invisible to all other users. However, the shadowbanned users will continue to see their own comments, hopefully oblivious to the fact that they’ve been shadowbanned. This is non-destructive in that changes are not made to the comments themselves. Shadowbanned comments are still saved to the database and visible to admins in the dashboard comments listing. All that happens is that a ‘shadowban’ flag is set in the user metadata.
If you disable this plugin, showbanned comments will become visible to all users.
For the latest instructions and more information, please see the <a href="http://anothercoffee.net/feenban/" rel="nofollow ugc">Plugin Homepage</a>
Licensing
All code is released under The MIT License (also known as the “Expat License” by the Free Software Foundation). Please see LICENSE.txt.
Although this plugin has been released under a license compatible with the GPL2 as stipulated by the <a href="https://codex.wordpress.org/Writing_a_Plugin#File_Headers" rel="nofollow ugc">WordPress guidelines</a>, users are encouraged to checkout the BipCot NoGov license from the Beastlick Internet Policy Commission Outreach Team: http://bipcot.org

FeenBan

FeenBan is a WordPress plugin for shadowbanning / hellbanning commenters.

WP-BlockYou vs FeenBan