I do think Peter Quill’s trauma tends to be a bit overlooked in fandom. When you realise how long the list of traumatic things is, and how many of those things are discomfortingly realistic I guess, it kind of… jumps out at you. (trigger warnings: child abuse , child murder and some discussion of rape. spoiler warnings: Infinity War.)

• Peter was born to Meredith, a human woman, and in GOTG Vol 2 he learns his father was a god called Ego. Ego not only killed millions of Peter’s half-siblings throughout the past millennia, he also killed Meredith when he realised he’d grown to love her too much. (Remind you of anything?) Peter had to watch his mother die of the cancer neither of them knew Ego had given her.
• The circumstances of Peter’s conception are… I think it’d be fair to say they’re the sort of thing that would haunt you. Meredith had a consenting romantic relationship with Ego and got pregnant with Peter, but Ego neglected to tell her what he really was (beyond “a spaceman”), what he planned to do with her planet, or what he planned to do with her child. Especially considering how young Meredith was – in the opening scene of GOTG Vol 2 the script gives her age as 18; she might have been even younger when she first encountered Ego – she was utterly taken advantage of by him. I honestly don’t know if you’d call it rape by deception, but it seems to be not a million miles off. Meredith’s trauma feeds into Peter’s, too. Had something terrible not happened to her, his mother, he wouldn’t exist. It’s a horrible thing to think about.
• Peter grew up a bullied kid, being picked on by schoolmates even as his mother was dying in hospital. Watching a parent slowly die of cancer is horrible at any age, and Peter was only eight.
• Peter’s too scared to hold his mother’s hand as she dies, something that haunts him well into adulthood.
• Immediately after Meredith dies, Peter is thrown into a world of cutthroat pirates and mercenaries. He can’t go home again, can’t see his grandparents again, and has to learn to steal to earn his keep. He grew up in a secure, safe place and now all that security has gone.
• Yondu loved Peter, true, but up until the last few minutes of his life he was an awful father. He may have thought that “beating the crap out of [Peter] to teach him to fight” was thoughtful parenting, especially considering his own background, but honestly… it’s abuse.
• Peter loved Yondu too, despite this, and then had to watch him freeze to death in the depths of space to save him.
• Ego not only killed Peter’s mother and millions of half-siblings that he’ll never know, he tortures Peter as well. At the same time he starts using Peter as “a battery”, he’s killing people all over the galaxy. In addition to whatever pain being used as a battery causes, Peter might have seen or even felt all those people die.
• After Ego turns to dust in his hands, Peter closes his eyes and accepts his own death, and would have met it if Yondu hadn’t saved him.
• The fact that out of millions of Ego kids, Peter was the only one
  who displayed the correct powers and was allowed to survive, that’s got
  to lead to some unbelievable survivor’s guilt. He’s essentially the last survivor of a horrible sort-of-eugenics program.
• Finally, after all that, Peter embarks on a romantic relationship with Gamora. She dies (or, I fucking hope, ‘dies’) at the hands of her own megalomaniacal god-like father, because he decided he loved her so much that she was a worthy sacrifice. Just like Ego had done with Meredith, after he abused and hurt her and Peter couldn’t stop it. He couldn’t stop it this time either.

Y’know after Vol 2, there was a brief wave of people saying “God, Peter’s been through so much, it’s amazing he hasn’t completely snapped.” That one scene in Infinity War which people are calling him a villain or a man-child over? That was him snapping.