3C 405 (Cygnus A)

This is the optical counterpart to one of the strongest radio sources.
https://www.stsci.edu/~marel/black_holes/encyc_mod1_q12.html

https://www.nrao.edu/archives/items/show/33384

https://ned.ipac.caltech.edu/level5/Carilli/frames.html

https://skyandtelescope.org/astronomy-news/mystery-object-in-cygnus-a-galaxy-1301201623/#google_vignette

At a redshift z = 0.056, this source is about 7600 Mly from Earth.