Lily knew that Rosedale had overstated neither the difficulty of her own position nor the completeness of the vindication he offered: once Bertha’s match in material resources, her superior gifts would make it easy for her to dominate her adversary.
There are no more uses of "adversary" in the book.
Show samples from other sources
Then, again, our military training is in many respects superior to that of our adversaries.
Thucydides -- Pericles’s Funeral Oration
Finally, it was rumored, there would be complete information-sharing among all of these previously disconnected and even adversarial entities, and when they were coordinated, and once all the health data they’d collected was shared, most of this made possible through the Circle and more important, TruYou, viruses could be stopped at their sources, diseases would be tracked to their roots.