GodThingFormerly
A Different Kind of Asshole
Sounds like a job for a creative physicist. Ever read THE WOUNDED SKY?
Decades ago, and I only recall the NCC-1701 approaching some cobweb-like alien space station at the beginning and a list of bogus physical cosmology citations at the end. Everything in between is a blur.
Even if it were possible for mere humanoid technology to affect something with the mass of billions of suns, that would make for an awfully long movie, since that "destruction" would take hundreds of millions of years to unfold.
Not if, A), the dead quasar in question was accelerated to ~0.99c by Freeman Dyson's "Gravitational Machine" composed of two co-rotating black holes of comparable mass at some point in its history, and B). it approached UFP territory perpendicular to the Orion Arm. In such conditions the relevant perturbations would occur within a matter of centuries, so if the Enterprise matched velocity with the quasar post-intercept using her impulse engines then relativistic effects would permit the crew to observe the cosmic ruination unfold in proper time over scant years. Of course, a major conceptual sticking point would be how something like that could get so close to the Milky Way without a galactic supercivilization (Metrons, Organians, Living Machines, etc.) intervening, although I suppose a skilled LitSF writer could probably think up a semi-convincing excuse beyond that of "They ran away."
TGT