If you want the descriptions of what it was like just after the Atomic bombings in Hiroshima, the source I read got their excerpts from "To hell and back: last train to Hiroshima." [I think it's factually fine. The original book got retracted but I haven't seen anyone object to the second printing, and most of the issues related to the stories of the Enola Gay or the science and not the stories of victims].
As I was reading these horror stories, there was something in my mind that kept just weeping. This was a terrorist attack. Not just against the Japanese but against the whole world. Hundreds of thousands of people died, either instantly vaporized or agononizingly slowly over the course of hours to years. Elderly, women, children, disabled, and even Korean victims of Japanese slavery. All of that was done so the US could intimidate the world [more specifically, the USSR]. It wasn't an unfortunate sacrifice, it wasnt a mistake. It was an act of pure and unfettered terrorism, that gets justified in schools and propaganda outlets.
And they wanted to do it again. Douglas MacArthur wanted to drop 50 along the Korean-chinese border, Eisenhower (or people in the government associated with him at least) essentially threatened the chinese with the same thing. The soviets were threatened on a scale of thousands of hiroshimas before the Cuban missile crisis.
The way I felt when I was reading the accounts of these attacks was the same way I felt when reading about the Nanjing massacre. Almost incomprehensible horrors.
I get not a lot of people will disagree with me here but I just had to get it out because fuck I'm depressed
Edit:I forgot to add. I know this wasn't the worst crime during the war. I don't feel like ranking crimes against humanity but the crimes committed during the Holocaust and the Japanese war of aggression in China were obviously worse. I just wanted to say that because occasionally I get accused of being one of those "Japan [as a whole] is a victim" people