All i gotta say is Alderaan, Malachor V, Katarr, and Nathema
Well I'll Give you Katarr, since it was destroyed by the Sith to blind the Jedi to them. But Malachor was destroyed by the Republic according to Kotor2, and Alderaan is in the future so doesn't quite count (yet). But I'll admit I can't recall Nathema, is it in the Clone wars Toons.
But if I was on a planet beginning with T and the Sith turned up, I'ld worry, Then run before they blew it up.