Synonyms for Unrivalled (same or very similar meaning)
WordNet sense 1 (eminent beyond or above comparison):
matchless, nonpareil, one, peerless, unmatched, unrivaled, unmatchableWordNet sense 2 (such that comparison is impossible; unsuitable for comparison or lacking features that can be compared):
incomparable, uncomparableFrom the ODE community, based on WordNetadd/edit