It had been a finale which was long foretold. After he acquired all the six Stones, Power, Mind, Space, Reality, Time and the Soul, Thanos had executed his plan, and this resulted in the wipe out of half the population.
Much to the horror of the Avengers, Thanos had emerged victorious. But this victory had come at a price as the Mad Titan was forced to sacrifice Gamora to get the Soul Stone. It is this scene that reflects a tragic end to Thanos’ Journey according to Joe Russo:
“It is [in the soul stone], it’s an orange world that they’re in. Because he’s in the Hero’s Journey in the movie, we did point that out that there’s a correlating journey in the film between Thor and Thanos. Certain characters make very human choices in the movie that are very tragic that shift the direction of the storytelling. Quill makes that choice on Titan when he punches Thanos in the face.”
Star-Lord was not the only person who was guilty of taking his eye off the prize as prior to Thanos’ snap, the God of Thunder, Thor Odinson had buried the Stormbreaker into the villain’s chest and realized that it was too late.
Joe Russo continued:
“Thor makes that choice when he plunges the axe into Thanos’ chest because he wants to tell him that he got him, that this is payback. If he had not made that decision, had he gone for the kill, they wouldn’t be in this situation. For Thanos at the end of the movie, this is part of his Hero’s Journey, we once again put him face to face with the only thing that he cared about, where he has to own up to the emotional cost of what he’s done in the movie.”