Pants on Fire
An actor’s ability to improvise depends on two things: his skills and talent, and his familiarity with the nature of the film and the character he portrays. As you may or may not remember, Tony Stark and Captain America didn’t quite see eye to eye when he returned to earth after losing Spiderman to the human dust bowl. So, it wasn’t surprising that he would be a bit emotional.
At the beginning of Avengers: Infinity War, the fractured relationship of Tony Stark, and Steve Rogers is more than apparent when Tony verbally assaults Cap by saying, “No trust” and then improvising the word “liar.” The crushing blow truthfully demonstrated how devastated Stark was over Thanos’ victory and the Avenger’s inability to save their fallen comrades.