public function country(){
        return $this->hasOne('AppCountries', 'country', 'country');
    }

Users::orderBy('id', 'desc')->country()->get();

Users(id, name, country_id)

public function country()
{
    return $this->hasOne('AppCountries', 'country', 'country');
}

Users::orderBy('id', 'desc')->with('country')->get();