4. Avatar 2
From the least likely breaker of Endgame's record to perhaps the most likely Avatar 2 is 10 years in the making and is sure to be a box office titan, but can it beat Endgame?
Avatar 2 will certainly have a large build up and anticipation on its side as well as a sure fire effect spectacle from James Cameron. Effect spectacles can be more profitable due to increased sales in more expensive showings, such as IMAX and 3D.
To its advantage Avatar is only a sequel to one film and therefore does not require the extant of viewing pre-release that Endgame required and as shown by its box office pretty much everyone saw the original Avatar. Combining viewers of the original film at the theatres and people who have enjoyed the film since would give Avatar 2 the necessary boost to dethrone Endgame.
The continued expansion of many Asian markets such as China and South Korea could also benefit Avatar 2 in its mission to be box office king. Endgame managed to beat Avatar's Chinese box office by a staggering $400 million, however a large percentage of this can be attributed to the growth of the Chinese market.
Nevertheless, questions remain of the devotion and size of Avatar's fan base, which is definitely smaller than that of the Marvel Cinematic Universe, and therefore the willingness of people to show up at the box office for Avatar 2.