Deprivation creates attachment disorder. Pick most any famous serial killer you know...even Hitler...and you'll find a child who wasn't nurtured, whose needs weren't met, and whose early years were colored by abuse and neglect.
Here: I just nabbed this off the first search hit for Hitler's childhood.
His father, Alois, was a customs official while his mother, Klara, came from a poor peasant family. Life was financially comfortable for the Hitler family but Alois was a domineering character and young Adolf frequently found himself on the wrong side of his father's short temper. At primary school Hitler was a clever, popular child. At secondary school he withdrew psychologically, preferring to re-enact battles from the Boer War than study. He left school with no qualifications at 16.
John Wayne Gacy
As a child, Gacy was overweight and not athletic. He was close to his two sisters and mother but endured a difficult relationship with his father, an alcoholic who was physically abusive to his wife and children.[9] Gacy seldom received his father's approval, later recollecting that, no matter what he achieved, he was "never good enough" in his father's eyes.[10] His father regularly belittled him, calling him "dumb and stupid" and comparing him unfavorably with his sisters.[11] Despite this, Gacy always denied ever hating his father.[12]
One of Gacy's earliest childhood memories was of being beaten with a leather belt at the age of four for accidentally disarranging car engine components his father had assembled.[13] On another occasion, he was struck across the head with a broomstick and rendered unconscious.[14] When he was six years old, Gacy stole a toy truck from a neighborhood store. His mother made him walk back to the store, return the toy and apologize to the owners. His mother informed his father, who beat Gacy with a belt as punishment. After this incident, Gacy's mother attempted to shield her son from his father's verbal and physical abuse,[15] yet this only succeeded in Gacy earning accusations that he was a "sissy" and a "Mama's boy"[16] who would "probably grow up queer".[17]
In 1949, Gacy's father was informed that his son and another boy had been caught sexually fondling a young girl.[18] Gacy's father whipped him with a razor strop as punishment. The same year,[19] Gacy was molested by a family friend,[16] a contractor who would take Gacy for rides in his truck and then fondle him. Gacy never told his father about these incidents, afraid that his father would blame him.[11]
Charles Manson
Charles later obtained the last name Manson from William Eugene Manson whom Kathleen began dating in 1934. Manson was a heavy drinker and would be missing for days at a time and the two divorced just three years later in 1937. As Kathleen struggled with her own alcoholic tendencies she too would go missing for days at a time leaving young Charles to fend for himself and/or with a variety of babysitters while she was bar-hopping and hanging around various men getting into trouble. Charles refers to his mother as a prostitute from what he remembers.
There's some for your consideration. I'll write more later if needed. This topic angers and upsets me so I'll take a little break. I would like to add that sometimes deprivation takes place through no fault of a parent at all. Early separations at birth, for example, due to medical or mental health complications can disrupt the attachment and bonding process that every child needs to develop into a whole human being.
The seeds are sown for the development of empathy from birth and forward. When you see a guy like that punching the stuffing out of a helpless victim, you are looking at a young man with no empathy. Why? Because he wasn't the recipient of empathy as a child.
The one and only thing that can change the course of these children is insight on the part of adults and widespread reform.
Okay...break now.