ITT: You must select a single country to completely eradicate.
Every single citizen of said country, past or present, is destroyed.

BUT

Any and all official territory of said country is gone, along with all resources and all of it's wealth (that isn't banked off-shore).
Any tourist, deployed soldier or other kind of foreigner caught within borders is also lost.
Every single year for the next century, this day will be the "X-country mourning day" in honor of this great cataclysm, while people will inevitably glorify it's history and what a great loss it was.
The culture of said country will live on in virtue-signalling tumblr mourners, eventually growing twisted and less accurate.