Light Yagami/Harry Potter
Light granted Dudley his affections. They weren't much, but Light knew how to form a bond with babies at a young age. He had read the books for baby Sayu. His mother had taught him how to hold Sayu, how to show his love in soft little touches, how to comfort her, how to show approval and encourage her development.
Dudley took his affections too. Diddykins thought it was only proper when his cousin treasured him and as he grew two and a half, Diddykins began to imitate his parent's behavior. That wouldn't do, Light had thought. So he cut short his first step and proceeded to the second. He ignored Dudley. When Dudley then began throwing tantrum's and imitating some of his Vernon's sneers, Light punished him.
Oh, Light was not cruel. He would never hurt children. Never. But just as baby Sayu had needed encouragement, she had also needed training and be taught to respect 'No'. Light had read up on that too, and learnt from his mother on how to convey disapproval to children without hurting them.
The basics of it was such: Carrot and Stick worked as well on children as it did on animals and adults. So did ingraining Pavlovian responses. In fact, it worked even better.
Light was never cruel to children, but that didn't mean he was a good person. After-all, Light was only human.