im going to take a guess and say that it is the largest man-made explosion ever. Tsar Bomba was detonated 4km above the ground by the USSR in Northern Russia and thats a picture of the resulting blast. Dropped from 10km with a parachute to enable the drop plane to get away, the blast was over 3 times as powerful as the U.S. best.
They had a special on the discovery channel not to long ago about it, I think they were talking to one of the pilots who dropped the bomb at one point or another. They told him that the risk of the plane not being able to properly take off was high and that the chances of them escaping their own bomb were relatively high. It was a neat special, it showed video footage of the bomb going off and the area after the impact.
Yeah they had to modify the shit outta the plane to carry the big bitch and the bomb had a parachute that would slow the fall from the 10km drop height to the 4km detonation height so the plane could escape the blast.