Cyber-bombs were explosive devices developed and used by the Cybermen. According to the Cybermen, they were the most compact and powerful explosive ever invented, capable of extreme destruction on a planetary scale.
Some Cyber-bombs were capable of destroying a planet, or all life forms on a planet (such as the Cyber-megatron bomb) (TV: The Invasion) and others were supposedly capable of destroying a TARDIS. (TV: The Five Doctors) The Cybermen planned to destroy Earth in 2526 to prevent the Cyber-Wars. The Fifth Doctor described this cyber-bomb as being powerful enough to make life difficult for the people who survived the blast. (TV: Earthshock)
Some time around the 29th century, a ship of Cybermen attempted to destroy the Planet of Gold, Voga. The Cyber-Leader stated that only two bombs were needed to "fragmentise" the planet. (TV: Revenge of the Cybermen)