The serial killer's son

The Demon King, no one knew the murders real name, but he was well known for killing, torturing, abusing hundreds, if not thousands of people. One day though, it says that he found a woman that he loved... but when she didn't love him back... he become even more crazy. He tried to make her love him back... but she never did, but she did give him a child.

He made sure that the child would be fine as she was pregnant, momentarily stopping the rape, abuse and torturing he forced her to go through as punishment for not loving him back.

When it was time to give birth, he drove her to the hospital for her to give proper birth. That was when she spilled the tea and secretly told the doctors who the demon king was... and he was arrested shortly after.

Because of the great injuries she had, she died shortly after and the child of the murderer, known as Meliodas, was adopted.

No one ever noticed the dark thoughts he had, the mental problems he had... before it was too late.