The largest galaxy ever found IC 1011 is 6 million light years wide. Compare its size with our Milky Way galaxy.
Adam Rifkin stashed this in The Universe
One of the top Reddit comments:
This is the supermassive black hole in the center of IC 1101 in SpaceEngine
A mass of 10 billion suns, with a schwarzschild radius of about 400 AU.
I also took this pretty picture from the surface a planet about 1 ly away