The theme where somebody that is good turns for the dark is one of my favorite movie themes.  What always happens in that theme is that somebody who started off as a good guy, turned to the other side for some reason, weather it's because they are losing it, or something big happens to them.  but what always happens after that is it effects everybody around them in a bad way, and eventually that person starts to become more and more isolated.

In the Godfather Micheal Corleone at first didn't want to have any part in the family business, but when his fateh rgets shot he goes to the hospital to save his father, and tells him "I'm with you now."  Then he gets punched by a cop, then decides to kill that cop, and the Turk, and from that point on he's all in.  At the end of the film he is the new Don, and his first wife has been murdered because of him.  In the 2nd one he loses control over the Corleone family, but has complete control of the mob, but he is becoming more and more isolated.  In the end of the movie he loses his 2nd wife Kay, and she leaves with his children.  He kills his brother Fredo, which makes him even more isolated.  In the 3rd one it shows how he regrets his entire life, and his daughter gets shot in the chest, by a man that was trying to kill him.  When he dies he is all alone, and all of the women in his life have either been killed, or they hate him.  That is an example of a story where somebody breaks bad, and it effects his whole life, adn everybody around him.

In Saw John Kramer broke bad as a form of release, and he was losing it.  His wife had a misscariage, and then when he was diagnosed with cancer he tryed to kill himself.  He failed, and vowed to spend teh rest of his life testing other peoples will to live.  He first tested the man who killed his unborn son, and then a few more.  He becomes a sociopath, and becomes known as the infamous Jigsaw killer.  His wife leaves him.

Breaking Bad is a cliche that gets used in a lot of trilogy's, and it is a fascinating theme to me.