Question about Black Holes mass

I know Sagittarius A is about 4 million times the mass of the sun.

Ton 618 about 66 billion times the mass of the sun.

So my question is. Could there black holes out there, whether in the observable or unobservable universe that is 100, 200 or 300 billion times the mass of our sun.

Thanks. Interested in your thoughts.

— u/DamnAlmighty