The single largest object (excluding galaxies) ever identified is S5 0014+81. Brace yourself for this one.
S5 0014+81 is classified as a quasar. Upon closer examination, researchers discovered a black hole sitting at its center. Scientists anticipated finding an average-sized black hole... but were stunned when they calculated its mass at a staggering 40,000,000,000 (40 billion) solar masses