In my mind the hardest criteria to meet in what you posted is wrecking all the buildings. It's actually a lot easier to kill off most or all of the human population and leave them standing.
The thing about the human population is that it's maintained through a really terrifyingly fragile infrastructure, and the more developed and urbanized the population is, the more true that becomes. Anything that sufficiently disrupts the developed world's ability to distribute resources the way it does currently for more than a few months could easily kill off most of the global population, but wouldn't affect the rest of the ecosystem all that much at all.
One simple way to do it that's been mentioned a few times is disease. Whether natural or artificial, if you kill off enough humans quickly enough, the infrastructure keeping most of the rest of us alive grinds to a halt and now we've got nowhere near enough food and clean water. The bigger the city, the worse the death toll would be. Populations in rural agricultural areas would make it through with the greatest survivors. Big cities would turn into mass graves that survivors would avoid (literally) like the plague.
The other way that's closer to Slarty's answer is a massive solar flare or Coronal Mass Ejection. You totally don't need another star going supernova, our own sun could do it with a big enough fart.
Something close to this actually happened in 1859. We got hit with a massive blast of solar radiation that caused northern lights to be visible as far south as Florida and put so much power through telegraph lines that they caught on fire.
Something on that scale today would be spectacularly destructive. The entire electrical power grid, everywhere, would be damaged or destroyed. Almost everything that RUNS on electricity that doesn't have mil-spec EMP protection would be damaged or destroyed. The solar flare itself wouldn't kill that many folks. Anybody on the ISS would be pretty screwed. Civilian aircraft in flight would be in pretty severe peril depending on where they were, how much fuel they had, and how skilled their pilots were.
The sudden destruction of the entire global economy would have a massive death toll though because most of the population of the developed world now only has maybe a few weeks worth of food, and no way to easily get more, and no way to rebuild the infrastructure quickly enough.
And that's assuming that some trigger-happy nutjob somewhere doesn't react to the business by starting a nuclear war on top of it, which WOULD get most of your buildings destroyed, but it's hardly necessary.