A host / super user account. Hosts have full permissions to all sites in the DNN instance.
Steps
Go to Persona Bar > Manage > Users.
Search for the super user account.
From the Show dropdown, choose Superusers to filter the displayed accounts.
Browse the list for the user account.
Click/Tap the ellipses icon for the user, then choose Delete User.
Note: Deletion simply makes the account unavailable and revokes user-specific permissions. You must also remove the user from assigned roles to revoke role-based permissions.
What to do next
(Optional) You can purge the user account(s) if you want to permanently delete the user account and its associated information.