Chapter 10 Install and System Administration for FortiOS 5.0 : Basic Administration : Administrators : Administrator profiles : super_admin profile
  
super_admin profile
The super_admin administrator is the administrative account that the primary administrator should have to log into the FortiGate unit. The profile can not be deleted or modified to ensure there is always a method to administer the FortiGate unit.This user profile has access to all components of FortiOS, including the ability to add and remove other system administrators. For some administrative functions, such as backing up and restoring the configuration using SCP, super_admin access is required.
See Also
Creating profiles
Global and vdom profiles
Management access
Adding administrators