I've seen it mentioned a lot that Kaz didn't believe Van Eck could hate his son so much as to want him dead, but I think there's something very satisfying about the way Kaz finally enacts revenge on him.
Kaz wants Van Eck to suffer. And how does that happen in the end? He makes sure Wylan inherits everything.
Kaz goes from not believing Jan could hate his child to the point of murder, to realizing the best revenge, the best way to make it hurt, was making Wylan heir. Poetic justice I say.








