Full SPOILERS ahead for Avengers: Endgame!
Iron Man dies in the final act of Avengers: Endgame. Utilizing the cosmic power of the Infinity Gauntlet, Tony Stark gives his life in order to snap Thanos and his army out of existence and save the universe from extinction.
Tony Stark’s lakeside funeral includes appearances by all of the surviving Avengers as well as Michelle Pfeiffer’s Janet Van Dyne, Samuel L. Jackson’s Nick Fury, Cobie Smulders’ Maria Hill, Marisa Tomei’s Aunt May, William Hurt’s Thunderbolt Ross … and one particularly noticeable teenager who’s there all by himself.
So who was that kid? Some heretofore unknown offspring of Tony’s? A distant relative? Nope. That teen is a character MCU viewers have met before.
Source: IGN.com Who Was That Mystery Character in Avengers: Endgame?