Actually, we do NOT possess the technology (unless you care to show me specs on machines capable of destabilizing more than 59,742,000,000,000,000,000,000,000 kg of super dense rock. Hint. That's extremely heavy and dense, and the energy required would be absolutely solar.) to destroy an entire planet. And an asteroid doesn't obliterate the Earth's surface. It vaporizes itself due to the atmosphere and actual impact with Earth, possibly a dozen dozen feet deep, maybe a couple times it's diameter around itself into dust which covers the Earth, which causes no sunlight, which devastates the plant life (alongside falling sediment and polluting waters), which devastates animal life, and it moves on from there, making Earth appear very barren. But Earth is still there. This is where people say, "What if we destabilize the core?" What do you mean destabilize? It's NOT stable. It's molten, it doesn't support anything, and constantly causes eruptions of pressure all the time. If something as simple as a nuclear bomb (read: ten nuclear bombs required to jettison magma from the core to the surface, at least), then the Earth would have destroyed itself.
Nova's (read Supernovae event horizons) destroy their solar systems just before dispersal. Unless you're considering a galaxy's core. Even then, it will not destroy an entire galaxy, though destroy it mostly. Since the core makes up pretty much almost half of the galaxy itself in mass. A single supernova working at one solar mass (read: our home star, "Sol") even if you were to triple it's energy, and make it expand three times as far, the energy it must overcome throughout the galaxy is more than one billion times itself, and the distance is so vast in the vaccuum, that it just would dissapate. And for the most part about galaxy cores, our galaxy doesn't sit right on top of it. If we did, our entire galaxy would've been pulled in by it's gravity, and destroyed all things in our galaxy. Blackholes ALSO do not destroy galaxies. Unless of course you're also talking about a galaxy core. But since it would have to pretty much explode first, it wouldn't destroy the galaxy either way.
Case in point. If the universe's celestial bodies were THAT fragile, with THAT much danger lying around them, the universe would never have been habitable for us in the first place. If you REALLY think that the structures prevading our universe are at THAT much of a whimsey, and you're that interested in knowing, I'd definitely recommend a slew of astophysics courses, backed by the chem, basic physics, advanced physics, and particle physics courses that would definitely elate a different story.