Avengers: Endgame features a touching connection to Betty Ross. The character was played by Liv Tyler in 2008's The Incredible Hulk. In the 2008 movie, Edward Norton portrayed Bruce Banner and Hulk for the first and only time. Mark Ruffalo came on board to take over in 2012's Avengers, and we have yet to see a standalone Hulk movie in the current version of the Marvel Cinematic Universe. With that being said, the Russo Brothers were able to put in a deep cut Easter Egg for Betty Ross in Endgame.
While doing press for Infinity War back in 2018, the Russo Brothers were constantly asked about the victims of Thanos' Decimation. The Mad Titan was able to wipe out half of the living universe with a single snap, thanks to the Infinity Stones. In an interview, the Russos confirmed that Betty Ross was one of the victims of the Decimation, which leads us to how it was ultimately reversed. But first, we have to go back and see what version of Hulk we have in Avengers: Endgame.
In Infinity War, we saw Bruce Banner and Hulk having an inner battle. Hulk was not willing to come out and do Banner's dirty work any longer, so he hid. Even when Thanos and his army were destroying Wakanda and killing fellow Avengers, Hulk stood his ground. In the time between the last movie and Avengers: Endgame, we learn that Banner and Hulk have come to an agreement, which introduces Smart Hulk to the big screen. The character is based on Professor Hulk from the comics. It's this hybrid version of both characters that wields the Stark Infinity Gauntlet and brings back half of the universe, reversing Thanos' actions.
This means that it was Bruce Banner and Hulk who brought Betty Ross back from the void. It's kind of romantic when one thinks about it, though it is not explicitly stated if Banner knew about Ross this whole time or not. Smart Hulk took some major damage when he snapped his fingers, showing he was willing to sacrifice it all for the universe and Ross. In the end, Tony Stark wield the gauntlet to take out Thanos once and for all, which ends up killing him. This shows just how strong Smart Hulk is, thanks to the agreement between Banner and the monster.
There have been whispers of Liv Tyler possibly returning as Betty Ross in the upcoming She-Hulk Disney+ series. That has obviously not been confirmed, but Mark Ruffalo has also expressed interest in having at least a cameo. For now, the Liv Tyler talks are nothing but rumors for the time being, but we should receive an update in the near future. The Russo Brothers, along with Christopher Markus and Stephen McFeely, were able to throw a lot into the three-hour movie and fans are still finding connections from within. There are probably a lot more that have yet to be discovered. Marvel Studios' Infinity Saga Limited Edition Box Set is currently sold out, but it includes some deleted scenes from Endgame and Infinity War that offer even more context. Hopefully they release a general version soon.