“We” can destroy the universe by cramming enough photons into a small enough space. There is a threshold at which the space time continuum breaks down, iirc. Alternatively we, as in we, humanity, could try dropping a single atom to a lower energy level, causing a ripple effect that will cover at least our solar system, possibly the next one as well.
I do not know how either are possible to pull off and statistic teaches me that it is unlikely that there aren’t any mad scientists out there trying to destroy the world, or more, so I’m confident someone else is working on it as I type.
Now I have to look up again how this stuff works, because I’ve actually forgotton the physics behind this stuff.