I rather like the MCU Iron Man, so I'll give this a go.
He's a man with a chip on his shoulder, and he always bears it openly. He has weaknesses, and pain, but he doesn't obfuscate or hide it, he brazenly challenges the people in his life to accept him for who he is, faults and all. You could almost say he puts his worst foot forward, never letting anyone else let him off the hook. It'd be tiresome to be his friend (I can sympathize with Pepper here) but there's a certain nobility in all this.
Before he becomes a superhero, this comes from living in his father's legacy. He was a genius engineer, but he was still in the shadow of his father. He hated this about his life, but he didn't hide it or try to change, he acted out, challenging the people around him to see him as his own (deeply flawed) man, not the inheritor of a great legacy.
Once he becomes Iron Man, he recognizes that his pain and frustration aren't all there is to his life. He still has to live with his dissatisfaction with himself, but he can do good for others.
By the time Civil War starts, he has a terrible new sin to bear: The creation of Ultron, and an indirect responsibility for the destruction of Sokovia. So he works with the UN to make sure this never happens again. He's completely aware of the problems he created, and he's come up with a solution. The Sokovia Accords aren't a response to what the other Avengers did, they're a response to his failures.
He sees the danger at the heart of the Avengers, and he knows that he's the walking embodiment of it. For all the faults in his plan, he's not a hypocrite. If the Sokovian Accords are signed, he isn't immune from the UN oversight, after all. He's supporting this plan to make sure he never makes a horrible mistake like Ultron again.
Tony Stark has a lot of personality flaws, but he's an honest person, often in a way the other Avengers aren't. He sees the danger presented by the Avengers, and he sees it most clearly in himself.