Extension of the theory of mutually assured destruction.
If a nation possessed a Doomsday machine, or system of nuclear weapons so formidable that any attack on it would lead to total global destruction, aggressors would be deterred.
David Robertson, The Penguin Dictionary of Politics (London, 1986)
Doomsday is a fictional supervillain appearing in American comic books published by DC Comics, commonly as one of the deadliest foes of Superman, as well as the Justice League. Created by writer-artist Dan Jurgens, the character had a cameo appearance in Superman: The Man of Steel #17 (November 1992) and made his first full appearance in Superman: The Man of Steel #18 (December 1992).
Doomsday ranked as #46 on IGN’s list of the Top 100 Comic Book Villains of All Time. He is best known as the only character to defeat and kill Superman in combat in The Death of Superman story arc “Doomsday!”. He appears in the film Batman v Superman: Dawn of Justice, where his vocal effects were provided by Robin Atkin Downes.