Why did Frank let Harmonica live?

Question

In the beginning of the film Once Upon a Time in the West (1968) the main bad guy, Frank, kills an entire family at a ranch including the youngest child of the family. The scene is meant to show how brutal and heartless Frank is as a villain.

Later, when Harmonica and Frank finally have their duel, we learn in a flashback sequence that

Frank killed Harmonica's brother when he was a child. In the scene, the brother is standing on a young Harmonica's shoulders with a noose around his neck as Harmonica struggles to help him balance. Frank sticks a Harmonica in his mouth to taunt him, and thus we learn the origin of his character. He ultimately is unable to keep his brother up and falls to the ground in exhaustion.

My question is, if Frank is a heartless villain who will kill a child so easily to keep from being named, then why did he let young Harmonica live?

Answer 1

I can only give possible interpretations:

• Frank was letting Harmonica live: as you point out, Frank only kills that child because he heard his name. His initial intention was to let him live. Thus he does not seem to automatically kill any witness to his criminal acts, especially if he does not consider him a potential threat. Similarly, it might be the case that he just decided to let Harmonica live because he was not his business, after all we never really know if or what was the reason for him to kill Harmonica’s brother. Given his character, he might also have wanted to keep Harmonica alive by pure sadism, to let him suffer the death of his brother.
• Frank wasn’t letting Harmonica live: again, as you rightly point out, during the flashback scene we see Harmonica falling to the ground due to exhaustion. They seem to be in the middle of the desert so it might be the case that, after Harmonica’s brother died hanged, Frank and his minions left, assuming Harmonica would also die there from the lack of food and water, or simply don’t caring at all about what would happen to him.

I don’t think the film ever clearly solves this point, and the viewer is left speculating.