General Order 24 of Starfleet is an order to destroy all life on a planet by orbital bombardment (as mentioned here and here). To quote the order:
If a commanding officer deems that a planet has been culturally contaminated to a point where correction is no longer viable and said culture now poses a direct threat to Starfleet personnel or Federation civilians, he may order the destruction of a planet’s surface to occur within a time limit set upon invocation.
In short, if the Starfleet captain feels so, he could as well order to destroy an entire civilisation.
Is there any ship in the Enterprise capable of executing such a feat single-handedly? If yes, is there some sort of weaponry aboard this ship (similar to the Death Star in Star Wars) that can eliminate all life on the planet?