The big one of endgame is Tony Stark commits the single worst crime in the history of the universe by “un-snapping” the half of the universe that was snapped by Thanos 5 years after they disappeared. No accounting for all the people who are dead in the meantime, no accounting for all the awkward conversations of “oh for me I just blinked and now you have two kids and a new wife” or “who are you people and why are you in my house where am I supposed to live now” all because he lacks the imagination to make the universe go back 5 years while keeping Pepper and his daughter the same.
The big one of endgame is Tony Stark commits the single worst crime in the history of the universe by “un-snapping” the half of the universe that was snapped by Thanos 5 years after they disappeared. No accounting for all the people who are dead in the meantime, no accounting for all the awkward conversations of “oh for me I just blinked and now you have two kids and a new wife” or “who are you people and why are you in my house where am I supposed to live now” all because he lacks the imagination to make the universe go back 5 years while keeping Pepper and his daughter the same.
Oh and
spoiler
he dies in the process too
. That’s probably more important to most people.