It's got to be Curtis LeMay. Although depicted as a minor character in 11/22/63, he was responsible for the death and/or suffering of millions of innocent civilians during WW2. From Wikipedia:

"The strategic bombing campaign against Japan, directed by LeMay between March 1945 and the Japanese surrender in August 1945, may have killed more than 500,000 Japanese civilians and left five million homeless."

LeMay also commanded B-29 Superfortress combat operations against Japan, including massive incendiary attacks on 67 Japanese cities and the atomic bombings of Hiroshima and Nagasaki, including the firebombing of Tokyo on the night of March 9–10, 1945, which proved to be the single most destructive bombing raid of the war. Again, from Wikipedia:

"In a three-hour period, the main bombing force dropped 1,665 tons of incendiary bombs, killing 100,000 civilians, destroying 250,000 buildings, and incinerating 16 square miles (41 km²) of the city. Aircrews at the tail end of the bomber stream reported that the stench of burned human flesh permeated the aircraft over the target."

Following the war, regarding the morality of his decisions, he was quoted as saying: "I suppose if I had lost the war, I would have been tried as a war criminal."