Tsar Bomba
RS-28 Sarmat is called a "superheavy" ICBM. Superheavy ICBMs date back to the UR-500 which was designed to deliver the 50 megaton (potentially, 100 megaton) Tsar Bomba warhead. The UR-500 was developed into the Proton which successfully launched the first living beings to orbit the Moon and return safely, on Zond 5.