Storm and Adversary only fought once, so what you mean by "everytime they fought"? CC chose to highlight Forge that go around with Adversary, but next round may have been focused on Storm with Forge out of the picture had CC stayed on the title long enough to cycle back to an Adversary story. Besides, even Adversary himself stated that Ororo was a worthy foe while it was obvious he considered everybody else outside of Ororo, Roma, and Forge as nothing.
Anyway, I state again, while it was never fleshed out why Adversary feared Ororo, Coates has set this story up to show what Adversary may have seen in her power to make him afraid.