When someone beats you to it...by seventy years.  Back in 2015, I wrote a story entitled "Crisis on A Dead Earth" in which alternate universe Green Lantern Kyle Rayner and Interceptor Kara Zor-El were called to investigate Earth-964, a world where nuclear war broke out in 1964 and due to the use of cobalt 'doomsday' bombs, eventually caused the extinction of all human life on Earth. It was a cross between Neville Shute's On the Beach end of the world novel, which had a similar premise, and an analogue of Earth-One c1964, which meant that some members of the Justice League were caught in the nuclear exchange and perished. It was also the homeworld of Captain Thunder, whom the actual Superman of Earth-One met in Superman 276 (April 1974), so it was intended as a sequel to that Elliot Maggin story. Captain Thunder returned to his world after a twenty one year absence, only to find humanity had been destroyed by the aforementioned nuclear war. He was tortured by the fact that everyone he'd known and loved had perished, as well as his entire world, and he wasn't there to save them:

forum.5earths.com/thread/306/crisis-on-dead-earth

So, I was reading a new book on Golden Age DC (and Fawcett), and came across this. Someone had already written a Captain Marvel story on the same subject- in October 1946!:

dc.fandom.com/wiki/Captain_Marvel_Adventures_Vol_1_66

In this one, Billy Batson was reading a WHIZ television story, when suddenly there was an emergency warning broadcast indicating that the United States was under attack from nuclear bombardment from an undisclosed source. (Good to see it wasn't attributed to the Soviet Union, either!)  Chicago is destroyed and the whole thing escalates from there.  Captain Marvel watches helplessly as a dying mother and her child die in his arms and at the end of the story, he's the last being left alive on Earth. It turns out to have only been a dramatisation of mercifully fictional events. 

Great minds think alike...