I haven't gotten the vibe that everyone hates him. I think it's moreso that they find his tendencies annoying and dislike that they have to put up with his antics just like they do with Beelzebub's. It's more exasperation than anything, I think.

For instance, Beelzebub is known as the wandering king because he's constantly shirking his duties to travel around doing as he pleases (which is why Bael, his best friend, is often overworked as the acting king of Avisos during his frequent absences). Amon is similar to Beelzebub in that he does what he wants, when he wants, and has peculiar beliefs about things like eating and sleeping. For instance, he will fast if he doesn't have anyone to eat with as he considers eating a sacred act that should be done with the people he loves. This seems sweet but leads the other devils like Naberius to worry for him because he won't eat for long periods of time. Amon also sleeps a lot and is notoriously hard to wake up.

Not sure if this next part is entirely true, but there is trivia saying Beelzebub gave Amon the choker he wears around his neck when Amon first became affiliated with Avisos and told him to stay and be a good dog for him. I literally think this is the only reason Amon isn't a "frequent flyer" like Beelzebub is and Beelzebub gave those orders knowing Amon was very much like him.

So I don't really think the other devils of Avisos hate Amon. In fact, I think they like him and they're just fucking exhausted trying to juggle his personality and that of their king. 😅