Hailstorms. Thunderclouds. Meteors.
One classic way in fiction of marking a character as a scary mofo is to give them the ability to call down ruin from the skies. It plays into that primal sense of wonder and fear people naturally have when they look up and see that vast, ever-shifting tableau looming overhead. It also implies quite a bit of power to be able to forego attacking directly in favor of just waving one's hands and letting the heavens handle the rest. Plus it's just really darn cool.
City of Heroes, of course, has its own share of powers that do this - mostly rain powers, but some of the available summons also fit the bill. So, fellow heroes, villains, and other assorted power-wielders, what's YOUR favorite way to drop the sky on some unfortunate sod?