Based on this self-regulating maximum rate, scientists at the Harvard-Smithsonian Center for Astrophysics, Massachusetts, and the European Southern Observatory, Chile, have calculated an upper limit for these mega-mammoth masses. Fifty billion suns, that's 100 000 000 000 000 000 000 000 000 000 000 000 000 000 kg, otherwise known as "ridiculously stupidly big" and triple the size of the largest observed black hole, OJ 287.

Wow! Are you sure there's enough zeros there?

There's a Hole in the Bucket, dear Liza

Its actually not the biggest thing in the universe. The universes terminal shock would be the biggest. The Aether would be bigger. Superclusters would be bigger.
There are voids that are bigger too.

Voids are indeed the biggest. There is more voidness in one grain of void than substance in 500 billions suns...

Avoid the noid