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I get you. He will always be a morally grey character even right up to the end (I appreciate that Zig didn't suddenly make him all reformed at the end). And yes he has done some horrible things.
Ash gets a lot of hate in the story for his strict discipline of Grayson but I agree with it, especially after Grayson's first offence. Ash's greatest fear was that Grayson would murder someone or be murdered himself.
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He was excited (ears flapping) at the thought of Dane losing his eyesight permanently. And even worse, at the hospital he had the thought of killing Dane. It was good writing to have these characters traits still be present but he overcomes the urge & checks himself and even admits it to Dane. So yes he did improve a lot but he will still be a morally grey character imho.

The closest clinical diagnosis for him is alexithymia.
He (and his twin sister) manifested as dominant alphas AT BIRTH, unlike the other Miller alphas. The pheromone surge when that happened fcked up his brain since then.
He's not slow or dumb, he's brain damaged. The "logic" behind his actions right now is obviously warped but you'll understand why he did what he did in the upcoming chapters.