Someone with more knowledge than I on this can correct me if I'm wrong, but things such as arrested development can be heavily informed by trauma, can't they?
Because honestly, I've just been taking it for granted in the case of show-Armand. That it doesn't matter that he was turned at 27 in the show instead of 17 like in the book. Because, as he tells Daniel in episode 2x05 the first thing he can ever really remember is being chased down by slavers in Delhi. Like, that is his first memory of anything at the moment -- being chased and captured by slave traders.
And that has been his first memory of anything, from when he was a child, for over 400 years by that point.
And let's be real here, Marius was in no way equipped to help Armand deal with all the trauma he went through after Marius found him and took him from the brothel. As we know from the books, Marius didn't fully understand why Amadeo couldn't paint anymore, as Marius had seen him do in his memories. It was the 15th-16th century Italy. They didn't understand things like PTSD and other trauma responses back then.
So if Marius wasn't equipped to handle Amadeo's trauma after taking him from that brothel in the book, why would Marius in the show be able to, just because Armand in the show spent 12 years with him before Marius turned him, instead of just 3?
And, on top of all of that, now imagine things like the whipping scene from the books happening with an Armand who is, in the show's continuity, slightly older. (Say, 21 or 22). And things like the bloody banquet.
And because of the now extended time between Marius taking Armand from the brothel and Armand's turning, the show has the opportunity to add even more incidents like the two above to Armand's upbringing.
Because yes, those two things were part of Armand's upbringing. Marius said it in Blood and Gold, the night he rescued a dying Armand from the brothel. Armand was alone; there was no one looking for him, no one for him. So Marius could "educate" (groom) him in the ways of The Blood with no one to tell him no and no consequence to it:
And so, in Marius' mind, that is what all of what we saw him do with Armand was -- from the oral sex that night in the bath, to the whipping, to the banquet... it was to "educate" (groom) Armand to be a vampire and his companion in The Blood.
And that means in ways that did not really hold any regard for human morality, never mind anything else.
Now... instead of just 3 years of things like that, as in the book, imagine all that -- and more! -- going on for 12 years. All on top of the trauma Armand experienced before Marius found him.
So, 17-years-old or 27-years-old -- why couldn't Armand have a case of arrested development going on with him on top of everything else?
And yes, knowing this, understanding this, about Armand doesn't absolve him of the things he's done. Even Armand himself, in the books, knows there is no absolution for it. (And I feel his TV show counterpart will get to that realization in the future as well.)
Again, the Vampire Chronicles are not about monsters regaining or seeking to regain their humanity. The older these vampires get, the less human they become.
And any human that comes in contact with these vampires always loses their humanity. Either resulting in them eventually being turned... or going crazy.
And this is why Armand is one of the most vampiric of vampires. The traumas he went through when he was a child were so horrific that most of his memories of his human childhood are now blocked. And then he was raised (goomed) by Marius during the remaining time he was human for the eventual time Marius would turn him into his vampire companion.
Again, this is not to excuse Armand for the things he's done. But knowing this about Armand, ask if you (the reader/viewer) can feel empathy for him, all the same.