This past March, scientists watched a Black Hole devour a star. It's roughly ten times the diameter of our Sun, but has about 8 million times the Sun's mass. NASA scientists recently made a great animation of what they saw for us mere mortals that have no idea what the people staring through the telescopes are talking about.
As for the unfortunate star, when it entered the black hole the energy in the star swirled around the black hole, forming a disc of light at millions of degrees and spinning at near the speed of light. The blast seen in the animation began at moving roughly 90% of the speed of light. The energy for this requires roughly one octillion (1,000,000,000,000,000,000,000,000,000) tons of matter moving at over 100,000 kilometers per second.