Hulk's appearance — which sees the green goliath sport a form-fitting, mostly black and grey suit with purple highlights as a nod towards his comic book counterpart's often-shredded pants — suggests Bruce Banner could take on his Professor Hulk persona, in which Banner pairs his genius with the Hulk's physical might.
Following his defeat at the hands of Thanos (Josh Brolin) in the earliest moments of Avengers: Infinity War, Hulk refused to come to Banner's aid when called upon in battle against Cull Obsidian (Terry Notary) and the Wakanda-invading Outriders.
Now that the universe has fallen victim to the Decimation — the official term for Thanos' erasure of fifty percent of all living creatures — Banner and "the other guy" could make peace, even if temporarily, to help win the day.
Banner ultimately stepped up as a hero without Hulk's help, donning the Hulkbuster armor he co-created with Tony Stark (Robert Downey Jr).
"People speculated whether there was some fear on the Hulk's part about having to face Thanos again but I think ultimately what it is is that he's tired of playing hero to Bruce Banner," director Joe Russo explained on the Infinity War commentary track.
Added co-writer Stephen McFeely, "With a movie with 23 named heroes that you know from other movies, one of the challenges is to give people the briefest complete arc. Banner has to rely on himself is essentially the briefest one line arc in this movie."
Hulk's decision to withdraw comes as part of a multi-movie arc playing out since Thor: Ragnarok, set to come to its head in Endgame.
"This was an interesting journey that we went on with Banner, trying to decide how to move him forward in the Marvel universe," Russo added.
"What makes him unique as a character is that there's a host body that is being fought over by two distinct personalities who hate each other. Both want control of the host body. We thought an interesting direction to take him in is, 'Well, what if Banner, who typically uses the Hulk to solve crisis situations, what if the Hulk were no longer interested in solving those problems for Banner?'2comments
"So, the relationship is becoming increasingly dysfunctional and that's what's going on here."
Avengers: Endgame releases April 26.