// disable the admin bar
show_admin_bar(false);

Alternatively you can go to wp-admin > All Users > Edit User > Uncheck option Show Toolbar when viewing site.

Hope it helps!

DELETE FROM wp_comments WHERE comment_approved = 0

Please back up your wordpress database before you make any changes.

This method filters the list output directly and prevents any title from showing. Add this to your functions.php file to remove the title from categories.

Open up the functions.php file in your child theme and add the following code. The code should be entered at the end of the file, just before the closing ?> if there is one.

function wp_list_categories_remove_title_attributes($output) {
$output = preg_replace('` title="(.+)"`', '', $output);
return $output;
}
add_filter('wp_list_categories', 'wp_list_categories_remove_title_attributes');

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DELETE FROM wp_commentmeta WHERE comment_id NOT IN (SELECT comment_id FROM wp_comments)

Just tried it on one of my website reduced the size from 151.52 MB to 44KB. You can always manually delete the akismet meta key rows.

Always be smart, have a database backup.