The Tsar Bomba is the most powerful weapon ever detonated, and that was in 1961. Interestingly even that weapon back then had a 100 megaton design. They decided

The Tsar Bomba is the most powerful weapon ever detonated, and that was in 1961. Interestingly even that weapon back then had a 100 megaton design. They decided to scale back the tested payload for a variety of reasons including enormous fallout and that testing such a massive weapon would be a suicide mission for the pilots dropping it.