Who wants to bet that Jack Noir (the overpowered one from the human session) and Lord English turn out to be the same guy?
Jack Noir doesn't have pool ball eyes and can't fit in the coat.
It's not the first time this theory's been proposed, but it fell out of fashion after it was revealed the demon that was chopping up the trolls' session was Jack Noir from the kids', whereas before it was assumed that them and Lord English were the same person.
That's actually part of the reason why I think its Jack from the kids session. It seems somehow fitting that he should be embroiled in a brutal gang war against his own dopplegangar (remember the intermission?), and it would explain why Doc Scratch is meddling in the kids' session when he made it clear that he did not actually need their help to let his master into the Trolls' universe, which implies that he could be manipulating them to some other end, such as creating his master, or what will become his master after some further transformation, in the first place (and while there was a subtle implication in the same conversation with Doc Scratch that Jack and Lord English are not the same person, Doc also made it clear that it should never be assumed that he's implying something, and I choose to believe that the implied non-identification of Jack Noir with Lord English is going to be something like the bit in Star Wars where Obi Wan says that Darth Vader killed Luke's father but then in the next installment it turns out that he was using an obtuse metaphor for the change in Anakin/Vader's personality.)
Also, at one point Jack is depicted as wondering how he will pass the time after he has destroyed his home universe; Destroying other universes seems like an obvious solution for one who has (well, may have) both the power and the inclination to do so.
As for fitting into the coat, that could be corrected either by some further metamorphosis or by simply commandeering the bunny's enlarger beam eye.
Also, like the Felt gang, he is associated with the color green.