Lore wise fallen are extremely resourceful, and extremely powerful warriors. Sure we beat a hive god. A vex time manipulater, and a powerful fallen. Yet there is a reason the hive haven't killed the fallen, there is a reason why the fallen so quickly took over territory on Mars from a cabal strong hold. Fallen are not push overs. And the house of kings has some vastly intelligent and powerful fallen, I will go out in a limb and say this. We have probably not seen what the fallen are capable of.