Hulk snapped his fingers in the Soul World.
Fast forward to a year later in cinemas - but five years later in the Marvel Cinematic Universe - and Avengers: Endgame deals with the aftermath of this event. The remaining heroes had to created a few branched timelines and resulted in the death of Black Widow, but Hulk didn't let this sacrifice be for naught. He brought back the snapped people, and then Tony died snapping his fingers to eliminate Thanos and his army.
In a deleted scene from Avengers: Endgame, Tony was also going to visit the Soul World because of his snap. He would've seen an older version of his daughter Morgan played by Katherine Langford, but the scene was removed after test audiences found it confusing. If Tony visited the Soul World with his snap, though, then it would stand to reason that Hulk did as well when he snapped his big green fingers. So what did he see? Well, the latest Screen Rant video featured at the top of this post explores some possibilities.
The one option that is the most obvious for Hulk to see in the Soul World is Natasha Romanoff (aka Black Widow). She was the one who was sent to recruit Bruce Banner for the Avengers Initiative originally, but their connection became romantic in Avengers: Age of Ultron. Even though that storyline didn't get explored much after, there is still something between them when they see each other in Avengers: Infinity War and Avengers: Endgame. And, since Hulk said that he tried to bring her back with his snap, too, that could further explain why she would be the one that he sees.
Bruce Banner and Hulk don't have many other connections beyond Black Widow, as he doesn't have any kids, but there is one other long shot possibility. Bruce's original love interest was Betty Ross, so it is possible that Liv Tyler's character is who he saw. There is no confirmation that Hulk even saw anything when he snapped his fingers in Avengers: Endgame, but if he did, it is likely he saw one of these two important women in his life.
