Delete all comments

Yes, go to “Comments” there will be a list of all your comments, and they’ll have a check box beside them. Check each box, or select the box at the top to select them all in one click, then in the drop down list at the bottom select “Delete Permanently”.

Now click “Apply Actions”.

You can go in phpmyadmin and on wp_comments table click on first icon that will open page with all comments tick the ones you want to delete and then click red cross