The problem with people using power synergy to get ultimate power is that outside of Pantheon and the CUI, there aren't very many parahumans that can facilitate it.
Cauldron (utilizing assistance from Pantheon) can do it. They wouldn't be a
conflicting faction, since they don't care who wins as long as it's not Scion, though they may still be classed as their own faction as far as Dinah is concerned.
Dragon (by which I mean
all of the Dragons) might be her own, although she's in much the same boat as Cauldron (whilst she wants Scion to lose, she's a
little more picky on who 'wins' and I doubt she'd help people like the CUI (CIU? whatever...) unless it was absolutely necessary. So she could be another faction if Dinah can see multiple singular entities as their own faction (which she
possibly can, since she saw Taylor separate from Amelia and if that's because Taylor had taken the canon Khepri route it's a lot like Dragon controlling multiples of herself, sort of).
The Thanda were supposed to be conducting their own synergy tests, weren't they? And they tended to have pretty powerful capes available to them.
We've got no idea what the capes in the Birdcage have been doing, but they were watching a few Endbringer fights before that got canned, so they may have picked up on it themselves.
Various 'eastern' countries could have a large selection of powers to draw on, though I can't make guesses here since we know virtually nothing about them.
The African warlords, perhaps? They have a large interest in not being taken out by foreign powers, and it would be interesting if the actions of Pantheon have made Africa a better place simply because everyone there is getting along more just in case Pantheon decides to pay them a visit.
Really, any significantly large landmass will generate enough parahumans that there's a high chance some will come along that have broken combinations, or at least can be used together to be massively more useful then if not.
*Edit*
Damn it, TanaNari! How
dare you quote the things I quote and respond to the things I respond to in your own thread!