Vince Everett's personality
In the movie, you see his personality change. They make it out like he's becoming a heal. But I can't really blame him. First of all, he was doing well in the beginning. He was working and making good money. Then all of a sudden, he goes to jail for killing a guy in a fight he didn't start, he loses all his money, and comes out of jail with nothing. There was also Hunk, who told him it was not only a jungle in the pen, but it was a jungle out there and worse. Prison and Hunk hardened Vince. I don't blame him if he came across like a jerk in the movie.
I blame Peggy a little too. She asked if all he cared about was money when she wanted to go out. His response to her was, "What else?" I feel like she never let him forget that he said that. She got romantic with him and then rubbed it in when she went out with Teddy Talbot. Then she never called him and when he was so happy to finally see her, she said she was only there to discuss him making another record. She was kind of stubborn and should've thought of his feelings too. In the end, when he's laying in the hospital, she finally tells him she loves him. You could tell during the movie that he loved her. Just by the way he went to see her the first time they got romantic, the way he was so happy to see her after so long, the way he acted towards her in the hospital. I guess in the end, Peggy believed Vince was a good guy when he wouldn't fight back when Hunk was beating him up. He was probably afraid he'd kill Hunk like he did the guy in the barroom brawl. Just my take.