Hide the WPMU DEV Dashboard

If you want to totally hide everything so its not visible to anyone then simply use the following in your wp-config.php:
define(‘WPMUDEV_HIDE_BRANDING’, true);

I've tried above configuration, but my default administrator still able to see it. How to disable it so that it is totally hide-out even from the default administrator. Reason being, this is a standalone WP from my client.

Thanks.