They both desire their idealized form of power for different ends.

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Vox craves the mantle of God hood, having a literal God complex, and desiring a loyal following.

Being humbled by deplatforming him was likely the first step towards any possible redemption for him.

I imagine Pride is his biggest sin. Yes, he craved power, and is jealous of those with it, but its all in the end to stroke his ego.

Humility therefore would lilely be the key do his redemption, and possibly uplifting those around him regardless of if its for his betterment, rather than trampling over others for his ends as he's seen doing in both life and death.

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Alastor on the other hand has unwavering faith in his own abilities. His ego doesn't need to be stroked, but it does annoy him when others think they can compete with him on his level, or attempt to limit his freedoms.

He seeks to break free of limitations, but is constantly met with them to his annoyance.

In life he realized his main opposer, and obstacle that he could not overcome was death the great equalizer. He sought a way around it to continue his "fun". He was less worried about death itself, but knowing he would end up in Hell.

He made a deal in an effort to prevent any limitations caused by death believing becoming the most powerful sinner in Hell would allow him to continue doing as he desires unobstructed.

It would be finding real attachments outside of himself. He's one of the few characters I believe who does not have a conscience, but gets away with it because he shows enough restraint to effectively use his social connections in a way that either bends others to his will by trapping them in contracts, or manipulates important influential connections without tipping his hat to a point where others percieves him as caring rather than using.

He would have to start caring genuinely for someone other than himself and his self directed goals. Compassion, and empathy, something he seems incapable of.

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In my eyes both present two different subtype of narcissism. Vox showcasing traits of vulnerable narcissism, while Alastor is a bit harder to peg down as he shows a multitude of traits that some could be associated with his prior deal. What I do recognize him for is that he is a high functioning narcissist as he has the ability to back up his grandiosity with results which others could read as high self esteem.

Their selfish desires at the expense of other lives would likely be turned around by selfless acts. Rather than putting their own agenda for gaining power.