The finale of Phase 3 of the Marvel Cinematic Universe was brutal. At the end of Avengers: Infinity War half of all life was completely wiped out. But, the good news for all of them is they only had to die once. It seems that Doctor Strange may have been the most abused, as he apparently died 14 million times in the movie.
The Russo Brothers seem to have spent every waking moment since April fielding questions about the way things came to a close for the Avengers. One question, recently posed by a fan as part of a video for Wired, asks Joe and Anthony exactly how Doctor Strange's review of all possible futures works. It seems that Strange wasn't able to simply view them, but he had to actually experience them, which means he died at the end of nearly every one. According to Joe Russo...
He has to physically live them and then die in each of them. And right before he dies, he has to reset it, as we saw at the end of Doctor Strange, and do it again and take copious notes each time he does it.
That's pretty brutal. I mean, you figure in half of them Doctor Strange died with the snap, but in the other half he survived. What happened after that is anybody's guess but you have to figure that any attempt to bring anybody back failed, likely leading to Strange dying then as well.
Of course, there is a minor problem with this. In the one possible future where our heroes win, Strange falls victim to the snap. Clearly, this means that he is capable of seeing past his own death, so he doesn't necessarily have to reset things after he dies, in fact, if he does that, he never sees the solution.
Strange has to exert an immense amount of energy to go into that state, and the amount of time he’s in this state, as we know from the history in his own standalone film, Doctor Strange, he could be in that state for who knows how long. So it could have taken Strange an immensely long time to actually review all these scenarios.
Technically this means Doctor Strange might have experienced everything we see in Avengers: Endgame, the five year time gap included, 14 million times. If you thought sitting through a three hour movie was rough, imagine doing it that many times, all in a row.