Make Hypermatter technology advance by a lot. Hypermatter is already able to exceep Matter-Antimatter conversion according to the novel, Death Star. So make a scientist have a huge breakdown in it, and now 1 ton of Hypermatter can literally give enough energy to blow up a Solar System 100 times over. With this new Hypermatter development your villain or whomever you're choosing is now making superweapons that can quite literally blow apart chunks of Galaxies apart.