Hannibal Lecter became a pop culture icon in part because he was gleefully engaged in the taboo act of cannibalism without any specific reason motivating him to be such an evil bastard. 2007 brought us Hannibal Rising, which explained that Lecter was a tortured youth during WWII who got tricked into eating his dead sister.
If we're going to call the young Vito Corleone scenes in The Godfather Part II a prequel, we'll go ahead and bestow the same status on the first 30 or so minutes of Rob Zombie's remake of John Carpenter's Halloween. The film delves into the childhood of Michael Myers, making crystal clear exactly how a young boy could commit such brutal murders. The short version is "He grew up in an abusive environment surrounded by a bunch of s****y rednecks."
Queue the tune from Deliverance.