THOR & ROCKET:
Thor's sense of humor has always come out of the fact that he's a displaced Asgardian on Earth, and doesn't understand customs. As such, he's in very interesting company amongst the Guardians who are ALL a bit like that. That being said, Thor's changed a bit because he's intentionally using that sense of humor to cover up MASSIVE emotional damage that he's experiencing, the same way that Tony Stark does, but Thor's never done that before now.
That's why it's especially poignant during Rocket's, "Time to be the captain" moment with Thor, that he calls him out on it. Rocket does the EXACT same thing, and had his own moment like that during Guardians 2, and it's precisely the kind of damage that he recognizes.
With Groot getting taken away, I can only surmise that the two of them will be closer than ever going forward. Not only that they'll be an intentional source of light and levity in the bleak wastelands that they've been left in, and our other humorous characters are in a pain that they can't cope with.
TONY:
Whether or not Pepper is still alive is gonna be huge on him, in addition to the fact that the whole dream about having a kid, and Peter disintegrating in his arms is really gonna mess with his PTSD. He's normally full of quips and other things, but I think that he's gonna have it REALLY hard to even attempt to be that side of himself. I think that what he's got is the reconciliation with Cap who just lost Bucky, and that the two of them are gonna be support for one another with nothing else around them.
BANNER & HULK:
Hulk's been our long enough in Ragnarok that he's experienced things other than just rage, and now he's properly terrified. That's gonna take some significant personal therapy to deal with between the both of them, and by the end of it, I think that we'll have a very interesting dynamic between Banner & Hulk, especially because Banner stood up to fight when Hulk wouldn't.
Even with Hulk properly on the table again and with Ant-Man/Wasp (assuming that the aftercredit of that film has some of them survive), and with Hawkeye possibly back in the mix, who's there? Who's left that's really taken all of the damage, and done nothing but hone it into pure purpose?
NEBULA & THANOS:
It's understated for the time being, but this film showed that Gamora was GENUINELY loved by Thanos, and she was unquestionably his favourite. Nebula is literally nothing more than a tool that he'll gladly torture to get what he wants out of his favoured daughter. This makes everything with her that much more painful, and I feel is going to be a MASSIVE motivator in the next film, and why she was left along with Tony. Not only can she bring him home, since she has a ship – but she's got all the motivation and more to do what it takes at any cost to bring him down. Whereas everyone else got hurt, she's already internalized all of that pain, and is laser focused to be able to bring him down. She's got the personal connection, and on top of that,
she's totally done it in the comics in a way that opens up for the arrival of Adam Warlock who was teased by Guardians 2.