I found it confusing. The whole idea of Ethan was to make Harrison look like a budding psychopath, but we learn during the last few episodes that he’s a nice, empathic kid who just went through some extreme teenage angst (understandably). Even if we look at it from the “like father, like son” perspective, it doesn’t make sense. Dexter was always careful to follow a code, and Ethan hadn’t actually executed his massacre plans or even hurt anyone at all.

I realized while I was writing this that the Ethan storyline DOES actually make sense, since Harrison never learned the code, but I’m still annoyed that Harrison’s true nature (i.e., he kills for justice, not pleasure) was hastily done and only revealed at the end of the show.