I feel like there's some really interesting nuance here too to bring up. In chronological order, first we see the development of his murder ritual. Locate the biggest fish (and I love the shark detail both in his business aggression, but his need to be the biggest fish), mimic said person, eliminate said person and the competition they represent (and any ability they could have had to change, and thus improve) and then "Improve" on that mimicry, using the adoration of others for that "improved" mimicry to validate his desperately low self esteem.
(and it's important to note for me here that this need for validation does not have a pseudo sexual element to it. He ignores the Beau of his first victim and the gaggle of female fans)
Then we see him in hell, and his personality is far removed from what it was at the end of his life. He's boyish and a bit shy but still enthusiastic and a bit naive. In hell. If anything he should have become more aggressive, more open about his violence, sharper and meaner.
People seem to think this is his "true" self, that he became like this in front of Alastor, let himself become vulnerable, and I disagree. In at least as far as this being his "core" traits.
Vox is so deeply insecure and in to dangerous a place to ever do something like confront his own true self. It's antithetical to who he is.
I think it's another mimicry. I think he landed in Alastor's territory, zeroed in on that fish, and the Vox in the flash back we see is the line he threw out to catch it.
I think Alastor was the first victim he chose in hell.
He's already reflecting Alastor in the flashback. From his mannerisms and cadence, and in most telling his clothes, he's already got drops of Alastor flavoring all over his personality.
And I love Alastor. I do. I read fics. I indulge. And I mean this in the most medically technical way possible.
Vox is not. He has narcissistic tendencies, and we'll get to that, but Vox is not.
Alastor is. A true narcissist.
Vox craves validation, Alastor expects it. While they look very similar, it's a very important distinction.
And a psychopath, that's important as well.
And narcissists love mirrors. Vox got close to Al through that mimicry, and plastering enough of that "new to the industry, yes man, sycophant" energy onto it to not trigger Al's irritation.
(to be clear, I don't think this is conscious on Vox's part)
And then Vox caught the feelings. Something about Al, and I'm not going to speculate what, but something about him led to enough respect and emotion from Vox to erase the competitiveness. Vox isn't going to show his "true personality" to Al because he's as disgusted by it as he thinks everyone else is. That isn't intimacy to him. What he wants form Al is validation. Because Al became the spotlight. Because Vox became content, excited even, craved even, validation from someone who mattered to him.
And I've seen people go "if only Al had accepted" or more accurately "If only Al had explained he was ace or been nicer about turning him down." And even if it's off topic I have to explain that that would have NEVER happened. It's contrary to his very personality. That's the tragedy. Al full on disassociates when slightly inconvenienced he's not going to suffer the discomfort of having someone actively attracted to and pursuing him around just for some mirrored validation.
Vox in modern times has now, having been denied validation from Al, slotted him firmly, a bit to forcefully and artificially, back into murder victim mentality. He's gone full chameleon (I'm just like you except I'm smarter sharper brighter newer!) (not to mention the very apparent physical and mannerific parallels) (don't get me started on the debate of how much of his narcissistic tendencies might be mimicry from taking in large narcissistic personalities) and even more funny, he's incapable of killing Alastor. He's willing to fantasize about it, but he is totally engrossed on NEEDING that validation from him before he kills him
(and on that note, the fact that Vox has been aggressively EDGING his murder ritual for decades is probably a decent chunk of his instability and a large factor in why he can't move on emotionally)
Which brings me to my ultimate point.
You talk about how the flashback recontextualized how we could see Vox's thoughts about Alastor's actions in having a public partner. And that's such a huge brain blast I'm still reeling. It's legit amazing and it's got me giggling. And I counter.
The flash ack should recontextualize how we see Vox's.
After rejected, Vox continues his murder ritual. Mimic, murder, improve, validation. Except he can't murder Al until validation is received. So he goes straight to improvement. And the show want you to focus on the TV vs radio dynamic. But what does Vox actually do?
He gets himself partners.
He becomes a version of Alastor who is "better", who has partners.
He needs Alastor's partnership to fail because his is "better" yes
But he needs Alastor to acknowledge it. He needs that validation, that subconscious proof that he was right. That he and Al could have ridden each other into the sunset. That they could have shone a spotlight on each other.
(and don't even get me started on the psychology of the scene that insinuated Vox slept with Val in front of Al. Val.... Al...... hm)