Remove WordPress comments from a specific user

You can remove all comments left by a single user by deleting them in bulk in the WordPress database.

Warning: Always make a backup of your site before making any changes to the database.

Sign in to phpMyAdmin.
In phpMyAdmin, on the left menu, select the name of the database your site uses.
On the top menu, select SQL.

In the box below, enter the following code:

DELETE from wp_comments WHERE comment_author_email = 'email address'

In the code, replace email address with an actual email address associated with the comments you want to remove. For example, if comments are associated with jane@coolexample.com, the code would be:
```
DELETE from wp_comments WHERE comment_author_email = 'jane@coolexample.com'
```
(Optional) If your table prefix isn't wp_, replace wp_ before comments with your actual table prefix. You can check which prefix your site uses in the wp-config.php file.
Select Go.
When asked if you really want to execute the command, select OK.

All comments from the specified user are now removed from your site.

WordPress Help