There are certain people who I want to smack upside the head.

Repeatedly.

Over and over until either the sense comes back into their thick skull, or they get knocked unconscious. Which ever one comes first.

You think you know someone, think you can trust them to be there for you, to give a crap about you as a friend, and then they turn out to be the biggest douche bag you've ever met. You get to sit by and watch as they not only hurt you, but hurt the people around you, including the one person he is supposed to love the most, supposed to care about the most; yet that one is the one he traumatized the most, did the most psychological harm to.

Why do people like to betray the ones they care about?

Yeah, this is going in the novel.