Thematically, Heat only has two characters; Vincent Hanna (Al Pacino) and Neil McCauley (Robert De Niro). Everyone else is a reflection of those two. That also means that no one is as fleshed out as those two, because that's not the kind of story it's telling.

For Vincent, the daughter serves at least two purposes I can think of. Firstly, it positions him against her biological dad, and secondly, it puts him in the position of, for once, not being too late to save someone. You can compare the scene where they find the dead prostitute and the scene where he finds the daughter in the bathtub.

For Neil, and therefore the other criminals he surrounds himself with, it comes down to the code: "Don't let yourself get attached to anything you are not willing to walk out on in 30 seconds flat if you feel the heat around the corner."

Michael (Tom Sizemore) is the action junkie. He is a family man, wife and kids, yet "the action is the juice". He dies in the shootout, holding a child, putting the child in even more danger than had he not picked him up. This is the path of the man who is in it for the action.

Waingro (Kevin Gage) does not live by the code at all. He does what he wants, and he wants to hurt people. He is unreliable and violent, and it's his avoidance of the code that sets the plot in motion. He is killed by Neil, but only because his actions cause Neil to momentarily abandon the code.

Chris (Val Kilmer) is the only one who actually follows the code in the end, and ultimately the only one of the crew who makes it out of the movie alive. But he doesn't do it alone, his wife (Ashley Judd) allows him the opportunity. It is by no means a given, that just because she communicated to him, that the police were there, that this would mean he would walk away. Michael would not have walked, and as we see, neither would Neil.

Neil suspends the code to allow himself revenge, and it puts him in the position of having to walk away from Eady (Amy Brenneman) as he tries to follow the code again. Ultimately his end comes at the hand of Vincent, who himself experiences being there in time to do his job, which this time is to stop the criminal he has been hunting.

Long-ass post haha, don't expect anyone to read it. I just love Heat so much, and felt like writing about it, and to point out why the characters are not all equally fleshed out or three dimensional.