[emilecantin]

I think that's where you're wrong. For a sufficiently advanced civilization, destroying another that's around our level would only entail destroying our planet. Hell, destroy the whole solar system to be sure. A "simple" way to do that would be to make the sun go supernova, or destroy it somehow.

How would you do that? There's a tremendous amount of energy already in it, it's releasing it gradually for now but what if there were ways to make it release all at once? One potential approach would be to throw something at it at relativistic speeds (you'd imagine accelerating things to near-lightspeed would be a pretty obvious milestone in the tech tree).

For an advanced civilization, this is pretty easy; they'd probably be able to do it routinely from a mobile spaceship so they don't have to give away their home star's position.