It was a damn good war. Nazis didn’t suffer nearly enough.
Ever notice how we are still chasing Nazi war criminals, but the Japanese war criminals still alive get a pass.
An article, "Would the atomic bomb have been used against Germany?" (if, say, the bomb had been ready in December, 1944), discusses possible answers, including a conversation with General Groves years later, and some discussion in the comments of what available plane could carry such a load.
IMO, if the bomb and a delivery system were available in December, 1944, it would have been an act of treason to refuse to order the bomb dropped on Germany.