Their emotional/moral weak spots
When he’s in a normal head space, it’s what he does when he’s in a near mental black out. The first few times it happened, he had no memory of what he had done at all. Now it’s all just hazy, like a bad nightmare when he comes to. But, pointing out what he’s doing in those states makes him break down because he honestly hates himself for it.
He’s terrified of becoming Chance and he fights it as much as he personally can.
Dark secrets/’skeletons in the closet
He was 15 the first time he saw someone die. They were drowning and instead of getting help, he just watched.
Everything he puts Ollie through. He doesn’t regret it as much as he should, but he regrets it as much as he’s actually capable of.
Things they’ll never admit
That things would be easier if he just gave into his nature. He’s afraid that if he admits it, he’ll give in and it won’t be pretty.
People they’ve hurt or indirectly killed, and how it affected them
For weeks after he watched someone drown, he was conflicted about it. On one hand, there was the deep set guilt that he should have done something, anything to help. On the other, it excited (in more ways than one) him to watch them struggle to stay above the water. It is what initially pushed him to get into med school though, even if he barely goes to class anymore.