(Freeze) A chilly day on Zeus 2

Zeus 2 was a world covered largely in jungles, with what little wasn't coated in dense forests being underneath oceans of fresh (yes, that's fresh: salt-free) water that still teemed with life anyway. A few deserts here and there, but mostly jungle.

Asteroid: I'm 'bout to end this planet's whole career.

Indeed, an asteroid zipped around the planet 3 times and then shot into space, but why did that matter?

Because the asteroid was pretty thicc. Thicc enough for its gravity to matter. Thicc enough that, as it zipped around the planet, it stripped the locations parts of the atmosphere it passed through of greenhouse gases.

2 weeks later and the planet was an arctic one, with trees frozen into position and hairy ice sculptures where people's pets had been. Some of the humans that either couldn't afford to or were unwilling to leave survived, resulting in many confirmations of the fact that yes: if a person is frozen enough you can shatter them by hitting them with a heavy blunt object... such as a shovel.

6 months later and the passive reterraforming (referring to any kind that doesn't insta-kill those on the planet) warmed it back up again. Nice.