The Time Heist accidentally created Doctor Doom
In Endgame, Tony and Cap stole 4 vials of Pym Particles from 1970. The Infinity Stones were returned, but those particles never were.
Imagine Hank Pym blamed Howard Stark for the theft. S.H.I.E.L.D. turns on him. Howard and a pregnant Maria are forced into exile, hiding in the mountains of Latveria.
Their son grows up with Tony Stark's genius, but without the Stark fortune. No Avengers. No Iron Man. Just a lifetime of resentment toward the heroes who destroyed his family before he was even born.
Tony Stark's face. Tony Stark's mind.
Victor von Doom.