This plugin allows Admins to type in the username of any user and it will bring up their permissions in a much easier to understand table.  General Permissions are in a separate tab than forum permissions because it can get long.  You can also see what permissions Guests have.  The plugin does use the language that is already built into MyBB so no additional language packs are necessary.

PHP 7 is required to use the plugin as is.  If you wish to use PHP 5 series, you must add this after line 171 of admin/modules/tools/permissionviewer.php

$prefixes = array();