##Nuke it from orbit.
Nuke it from orbit.
It's the only way to be sure.
This might be a pretty boring answer, but if your obstacle is a city, and removing the city would give you success, then that problem is fairly easily solved. Bombing cities has been the best way to destroy cities for a long time now- why change the status quo?
Yes, yes I see
PS: No nuclear weapons. I have a severe allergy to nuclear detonations.
So conventionally bomb it from orbit. (A much less catchy and memetic headline though.)
We have pretty big non-nuclear bombs. And who says you have to just use one anyway?
Or not from orbit: drone bombers would probably be more effective anyway.
If you actually want the "orbit" part, or have something cooler than normal bombing- just drop stuff on them from space. It's called kinetic bombardement and I hear it's pretty deadly.
PS. Loudly playing The Bieber might have more effect than you give it credit for. There are such things called sonic weapons, after all.