Super Users are users who belong to a specific portal user group and have the ability to delete other users with similar user information, such as a company ID or group ID specified in an external user request field. Additionally, Super Users can also access an expired portal's User Settings and Portal Settings menus.
In the Configuration module, create a user group for Super Users. When the portal is created, you will assign this group as the user group containing Super Users.
See the System Administration documentation for more information about creating user groups.