If your company has external admins and you want to revoke access to any of them, here are the steps to do so:
1. From your company dashboard, click Settings > External admins from the left-hand side navigation menu.
2. From the list of external admins, click the button arrow corresponding to the email of the external admin.
For each external user, you can set access to either Admin or Viewer. If you want to delete an external admin, click the Delete icon.