Oppenheimer
There will have to be many more watches, and a read of American Prometheus to fully understand the impact of both this film, and J. Robert Oppenheimer's life at large, but I will attempt to review it by using a few scenes that really stood out to me. One thing I can say is that Nolan was right in saying that Oppenheimer is the most important person in human history.
The Trinity testing in Los Alamos is commonly considered the beginning of the Atomic Age, as well as the beginning of the never-ending war machine that is the American military industrial complex. Even Eisenhower (not depicted in the movie but had very much of a presence at the time) warned of this of course, in his farewell address in 1961.
The first scene is this: Robert, a man who is experiencing hallucinations of the end of the world due to his creation, enters the Oval Office and meets with President Truman. He tells Truman that he feels he has blood on his hands, to which the president responds (after crudely flapping a handkerchief in front of him) "the Japanese don’t care about who built the bomb. They care about who dropped it. I did that.” He deems Oppenheimer cowardly for wanting to prevent further development of the H-bomb project.
It's clear from the scene and Oppenheimer's reaction to this information that Oppenheimer not only unleashed a horrible weapon of mass destruction, but has also ushered in a dynasty of warlords that would last to this very day.
The second scene solidifies this: we finally learn what Oppenheimer says to Albert Einstein that causes the latter to brush off Strauss. It's a conversation about the 'near-zero' chance that dropping the bombs start a chain reaction and ignite the world (in the literal sense). When Einstein scoffs, Oppenheimer remarks that they have.
And that is the significance of this man. He transcends his era, and is one of, if not the most prevalent node in the history of humanity itself.
"I am become Death, the destroyer of worlds."