When black holes consume enough and get large enough, they eventually become what’s known as supermassive black holes. These supermassive black holes can be millions of times the size and mass of our Sun. http://astronomyisawesome.com/galaxies/life-cycle-of-a-massive-star/
The giant black hole in the middle of our galaxy stays pretty quiet most of the time, flaring up only occasionally. But it is due for a burst of activity any day now, as a large cloud of gas and dust continues to spiral toward the heart of the Milky Way.