Light Yagami/Harry Potter
Here he was, Light Yagami, now named Harry, Freak, Boy and a combination thereof, ex-God of the New World.
And here they were, a suburban British couple with less brain cells combined than an amoeba trying to abuse Light as if they were doing their God a favor.
Light was half tempted to kill them for their daring.
He thought of cyanide. It would be ironic, using ground poison found in the core seeds of a Shinigami's favorite food to kill his new foster family.
Maybe some poison from the cleaning supplies (cleaning the filth of child abusers instead of toilet scum).
Perhaps Petunia's cosmetics. Despite saying otherwise, Petunia's make-up wasn't exactly the expensive, dermatologist recommended brand. Light had heard enough from horror stories from Misa to know how wrong cosmetics can go.
A heart attack inducing mix of Vernon's favorite alcohols? There was a serial killer back in 2006 who worked as a bartender and used to kill his victims that way. Light had handled the case as L, amusingly enough.
Or perhaps simply putting sleeping pills in their food and then killing them with carbon monoxide poisoning? It would take a while for Light to plan that one out, to kill Vernon and Petunia without burning the house down around them, keeping Dudley and himself safe and providing safe alternative residences for them both. Orphanages may be outlawed in Britain but foster homes could be just as bad.