The most powerful breaks I remember were David Howard, Danny Medina, George Breedlove and Wade Crane. There were no radar guns back then. I suspect they were all capable of breaking over 30 mph.
Then of course there is the mighty Mo Fo Yung. He is in a separate category for good reason. No one is even close to his speed on the break shot. He once broke the balls so hard that a cop who was outside using a radar gun came inside to see what was making his radar gun top 60 in a school zone. We directed him back to Mo and he proceeded to put the gun on him. 62, 64 and a final 66 and he got a ticket! The cop told him to slow it down since there were children playing in the area. He was afraid they would get hit by flying debris. MO FO YUNG LIVES!!!