Light Yagami/Harry Potter
When Light had first started living with the Dursleys, he had quickly realized two things:
First, Petunia and Vernon Dursley loved their darling little Diddykins.
Second, Petunia and Vernon Dursley feared him more than they feared for him.
In the beginning, it made Light see the couple as reasonable humans. Sure Vernon complained about his job and Petunia gossiped. That was standard suburban couple behavior. Sure they wanted to stunt his development for some reason and that's why they kept feeding him less than Dudley. It helped that Dudley was a big eater by genetics- one look at Vernon was all it took to come to that conclusion- and so they weren't actually starving him, not really. Being fed less than Dudley actually kept him healthy.
But when that fear for him turned into an ingrained habit of insulting him at every turn? As if every accident, every moment of bad luck or general clumsiness on any household member's part was Light's fault? When they tried to shove him in the cupboard under the stairs the second he turned two?
Yeah, Light knew a downward turn when he saw it.
Vernon and Petunia Dursley were turning into fanatical child abusers.
Light was, despite himself and his situation, more amused than angry.