Well... here's how it goes actually.
I'm using post-Geed movie Orb who is already well beyond baseline. Since we know that Orb Dark is somehow just as strong, and his elemental powers is comprised of 4 Crystals, one of which is Grigio. Whom we know will fight the brothers.
So basically, Orb Dark = Orb = Geed movie Zero Beyond who is > Series version who is slightly < Belial Atrocious who in turn, received nearly the entirety of King's power.
Thus, Orb Dark should be > 4 Monster Crystals, 1 of which is Grigio who is = both Rosso and Blu.
I'm sorry if this is a bit confusing, looked better in my head.