What is a nuclear missile? How good is it?

A nuclear missile is a missile with a nuclear warhead. In theory, power can destroy a city (of course, it depends on the equivalent size of a nuclear bomb), but in practice it is impossible to achieve such a great effect. For example, in World War II, the power of nuclear bombs declined because the mountainous areas in Japan played a certain role as a barrier, so the power of nuclear bombs depended on the actual environment and the equivalent size of nuclear bombs.