On October 30, 1961, Tu-95 Bear bomber guided by pilot A. E. Durnovtsev(he was made a Hero of the Soviet Union) flew towards Novaya the Zemlya Island in the Arctic Sea. That day will forever remain in nuclear history as a day when the most powerful thermonuclear has been detonated. Tzar Bomba (King Of The Bombs) yielded 50Mgt. Originally US estimated its yield as 58 Mgt, however resently declassified Russian materials show 50Mgt figure. Apparenly US overestimated bomb power.
Probably only first nuclear and thermonuclear bombs caused as much reaction as Tzar Bomba did. Tzar test was a parachute retarded Airburst at 4000 meter altitude.
Full history here.