admin only can log from a certain country
I would use the Smart IP module (https://www.drupal.org/project/smart_ip), you can add an extra validation on the login form that checks the country (https://api.drupal.org/api/drupal/modules!node!node.api.php/function/hook_validate/7).

You should check if the username exists on validation, when it exists you can check it's role and when it's the administrator role you make sure only users with the IP of your selected country can log in as admins.

There might be easier ways.