Question: which country has most powerful hydrogen bomb?
Answer: The Soviet RDS-220 hydrogen bomb (code name Ivan or Vanya), known to the Western nations as Tsar Bomba (Russian: Царь-бо́мба, tr. Tsar'-bómba, IPA: [t͡sarʲ ˈbombə], lit. 'Tsar bomb'), was the most powerful nuclear weapon ever created.