Grayson is deadass evil bro

Grayson is a psychopath ( problems with recognizing/ understanding emotions etc.), but he is not evil.
Grayson actually cares for Chase and wanted to help him, but Grayson and his understanding of help is a big problem, always has been. So he managed to cause his brother trauma and made him hate him.
You can call Grayson crazy, insane, an asshole etc., but he is not evil.

What you wrote is not what happened. Yes there is thst dog thing, but bringing the dog was a paniced reaction to Chase's first rut.
And Chase only thought it's possible, because he remembered a dog.
And he uses it to get Chase to the pheromone parties, where they take out his pheromones by injected after he passed out.

OK thanks just to clarify I don't know anything about the plot or novel AND you said "And he uses it to get Chase to the pheromone parties, where they take out his pheromones by injected after he passed out." I think that pretty much is enough to label him as bad. No offence but just look up the word evil it aligns with how he forces him to an orgy when he CLEARLY doesn't want to be there
evil
adjective
uk /ˈiː.vəl/ us /ˈiː.vəl/
Add to word list
B2
morally bad, cruel, or very unpleasant.

So it's less evil to watch your brother go insane or die (because this will happen, if you don't release pheromones for a long time), while you know how this can be avoided by medication? Seriously?
Chase is not releasing pheromones willingly, also he has no controle when in rut. He is not goining to the hospital on his own, if he would there wouldn't be any need.
And Chase is not only going because of the dog threat, but because he knows that his father will take care of it if he doesn't go.
And at those parties are doctors present, they never force Chase to have sex, he just passes out because of the pheromones floating around. And they use an injection.

Is Grayson good? -no, he isn't.
But he is not evil, because there is no malicious intent behind his actions.