And the duo credits both Spider-Man actor Tom Holland for his amazing performance, but also Robert Downey Jr., who they say worked with Holland to get him to that devastating place of hopelessness.

"If I remember correctly, it was [in the script] 'I don't feel too good.' Tony looked down at him. He said, 'I'm sorry' and disappeared," Joe Russo says on the commentary track of the moment after Thanos (Josh Brolin), equipped with the all Infinity Stones, snaps his fingers, killing half the universe's population.

"It wasn't as drawn out as this," Anthony Russo interjects as they watch the scene.

It was Downey who kept pushing Holland for more, according to the brothers.

"At the end of the day, he kept driving: put more and more emotion into it, and just went up to Tom and said, 'You don't want to go because you're a child. And you're using your strength as Spider-Man to fight this,'" Anthony Russo says. "And then that was the performance that came out."

He adds, "It was a pretty spectacular performance for a 21-year-old actor."

Avengers: Infinity War is available digitally now and on Blu-ray on Aug. 14.