When matter infalling to a black hole, it spirals and forming an accretion disc. For friction and spinning property of black hole, this region's temperature goes to million to billion kelvin. At centre where quasar is, gravity turns into light and high velocity (nearly equal to velocity of light)relativistic jets are emerged. That quasar for milky Way galaxy is 1000 times brighter than that of milky way itself. It can shine whole galaxy.
So the answer is SMBH powers the brightest object (Quasar)in the universe.
Image source: google