Compare that to a thermonuclear weapon which is in the range of 75 to 49,000 kilotons of destructive power. Used on a densely populated urban center like New York City or Tokyo, just one weapon would kill millions of people and produce millions of casualties.
Those numbers are devastating enough, but the real nightmare is that the number of thermal burn casualties greatly multiply with a thermonuclear weapon relative to a simple nuclear weapon.
A typical serious thermal burn injury in a well staffed hospital takes three to four medical personnel per patient to provide adequate care. When we have hundreds of thousands of surviving burn patients due to an urban thermonuclear detonation, we are not going to be able to treat even a tiny fraction of them.