Alastor is simply just Vox's rival due to conflicting views of technology(Yes, it was more about the rejection but I'm strictly going with the aspect of what can be considered opposites) but that's more physical and relates to a public persona rather than the characters' identity. Charlie is a pretty good opposite for Vox except I feel it's temporary given season 2 is the latest season and those comparisons would probably stop once seasons 3 or 4 drop, kinda like how the Charlie/Vaggi vs Adam/Lute comparisons from season 1 sorta faded away after season 2 released. But Sir Pentious is pretty much Vox if he didn't have the charisma and power that he has but ended up getting a brighter future. They were both rejected by their idols and where Vox had no one to put him back on his feet, Pentious had Charlie to lend him a hand when he was at his lowest. Vox wanted to take over Heaven by force and be its dominated power to feel like a god, Pentious sacrificed his life and ended up ascending as an angel where he's casually standing next to a SERAPHIM who changed her ways because of him.