One of the many things I love about Leverage is how they give you bits and pieces all throughout the shows to let you learn about the team and their pasts slowly, not all at once.
I mean, Eliot is my favorite. My absolute favorite. And one of his defining characteristics is that he's angry at the world. All the time. Except when he's fighting. When he's fighting, he is absolutely in control, and everything becomes crystal clear. He's taken the anger and the pain and the violence inside of himself and focused it on doing good.
And you can see glimpses of where all that comes from. Like, in Order No. 23 Job, when he saves the kid who's being abused by his father. You can see it in the way Eliot looks. The way he moves, the way he recognizes the symptoms when no one else does. Eliot came from home a violent home, and he knows that it broke him in highly significant ways, but with the Leverage team he has a family. Highly whacked and dysfunctional, but they're better together, and they make each other 'normal'.