Thor: Ragnarok - What The Ending Really Means

6. Bruce Banner Vs The Hulk

Throughout his appearances in the MCU, Bruce Banner's defining conflict has been around his battle to control Hulk (though confusing it turned out that he actually is in control and can call on the monster at will to begin with). His fear - which led him to Sakaar accidentally - was that he would lose more of himself and be unable to keep Hulk in check, after his rampage in Africa in Age Of Ultron.

Thor: Ragnarok continues that thread further with Hulk fully in control (as Bruce Banner says, he doesn't feel like he had his usual hand on the wheel) , and then further exploring Banner's fear that he'll continue to lose himself. Sure, it's all explored quite humorously, but it sets the stall for Hulk's arc to focus on how he deals with his return to Earth where he is "hated" in his own perception and also how he deals with the possibility of losing control again.

However you look at it, this is intriguingly set up for a couple of things. Firstly, Hulk still has feelings for Black Widow (as he showed when her recording played in the Quinjet), he still has to face people who hate him (General Ross is still active in the MCU) and he's susceptible to losing control. If Thanos doesn't use that last point against him, it will be VERY surprising.