i feel like theres gotta be more too, right? like his bird died and that's why he's an asshole? isn't there the dog thing too?
The main reason he is an asshole is, when he manifested as a dominant alpha. That was in his case after puberty. It affects their personality, he seems to have anger issues (like Keith Pittman) that result in him being violent.
Probably his medicine also affects him and him not releasing pheromones those phromones are like poison for dominant alphas)
The other things are his traumas. That are based on this family not understanding him, not reacting in the right way, hurting him because they didn't understand him. Making him an outsider. Resulted in hating his family. Having trust issues etc.
His dominant alpha siblings all manifested too early, which resulted in them having problems with understanding emotions ( Grayson for example seems to have a heavy case of Alexithymia + other issues) etc. So they don't understand Chase.
His alpha father also has problems, because he damaged his brain, resulted in him not feeling emotions anymore aside for his partner.
The dog trauma was caused by one of Grayson's crazy attempts to help. Resulted in Chase's fears of dogs, and losing controle while in rut, afraid of not remembering.
The toxic masculinity in his family ruined his childhood. He was just sad his pet birdie died and they all treated him like he was crazy for crying over it.