The events of Avengers: Infinity War proved that despite his earlier stance on the matter, Bruce Banner (Mark Ruffalo) wanted to be the Hulk. For most of his arc in the MCU, Banner struggled with having the green-rage monster as his second persona. In The Avengers, he poignantly recalled how he tried to kill himself by shooting himself in the mouth just so he could also rid of the Hulk, but that didn't happen as his alter-ego came out and spit the bullet out. Avengers: Age of Ultron further tackled this issue by delving deep into Banner's psyche with regard to having to share a physical entity with the Hulk. However, after a few years of spending in the Hulk's body, he eventually got the hang of it and might have even developed a liking for it.

Banner was already the Hulk for two years when Thor (Chris Hemsworth) met him in Sakaar in Thor: Ragnarok. At this point, the green-rage monster had already learned how to communicate with words, proving just how long he'd taken over his human alter-ego's body. After the Quinjet he used to flee Earth at the end of Age of Ultron instigated Banner's re-emergence, the scientist appears to have no plans whatsoever bringing back the Hulk because of fears that he might not be able to come out for another long period of time. The only reason why he transformed again was because Thor and the Asgardians desperately needed assistance in fighting Hela (Cate Blanchett). So, when Banner finally took over his body again at the beginning of Infinity War, one would assume that he would be content in keeping his human form, but his decision during the Wakanda battle in the movie implies otherwise.

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As the Earth-bound heroes scrambled with a way to keep the Mind Stone away from Thanos (Josh Brolin) in order to keep Vision (Paul Bettany) alive with the Infinity Stone, they sought the help of the Wakandans, particularly Shuri (Letitia Wright). T'Challa's (Chadwick Boseman) genius sister revealed that she was able to extract the gem from the Android's forehead, but it wouldn't be easy as they were pressed with time as the Mad Titan's minions closed in on them. Banner was instrumental in creating Vision, as he worked closely with Tony Stark (Robert Downey Jr.); he even acknowledged this as they were spitballing ideas with how to handle the situation earlier in Infinity War. However, when it came down to it, instead of helping Shuri with the procedure, Banner decided to be at the forefront of the battle even when there was very little he could do to help as he was unable to bring the Hulk back out. He took his chance piloting the Hulkbuster, which he initially struggled with.

Bruce Banner next to the Hulkbuster Gauntlet in Avengers Infinity War

Granted that Banner did destroy several Outriders and even took Cull Obsidian out, there's an argument to be made about the character being more useful had he stayed behind and assisted Shuri. With a second pair of hands to help detangle the intricate link between Vision and the Mind Stone, not to mention his knowledge of the Android, they may have been able to speed up the process, in time for Wanda (Elizabeth Olsen) to destroy the Mind Stone before Thanos got to Earth. Banner's choice at this important juncture in Infinity War indicates that he still longed to be the Hulk, perhaps much more so because he couldn't get him out. Unlike previous instances, there was no need for him to join the battle; there were plenty of other heroes who were more well-equipped than Banner, not to mention the whole Wakandan army and weaponry at their disposal.

With Banner and Hulk now combined in the Smart Hulk, it's unclear if Marvel Studios still have individual plans for the character. At this point, the only lingering narrative they haven't tackled is how the two personas were able to merge together during Avengers: Endgame's five-year time-jump. If they decided on exploring this time period, they might also want to explain why the Hulk refused to come out Avengers: Infinity War as explanations regarding this phenomenon from the filmmakers are a bit lackluster.

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