The largest explosion humans ever engineered was deliberately held back

In October 1961, the Soviet Union detonated Tsar Bomba, a hydrogen bomb roughly 1,500 times more powerful than the combined force of the Hiroshima and Nagasaki bombs. Engineers had already halved its planned yield to limit fallout, yet the shockwave still circled the Earth three times. It remains the most powerful man-made explosion in history, and the design was shelved immediately afterward.

— Richard Rhodes, Dark Sun: The Making of the Hydrogen Bomb — 1995
Go deeper: get the book →