Adjectives

(s)odd, unmatched, unmated, unpairedof the remaining member of a pair“unpaired socks”, “an odd glove”
(s)matchless, nonpareil, one, one and only, peerless, unmatched, unmatchable, unrivaled, unrivalledeminent beyond or above comparison“matchless beauty”, “the team's nonpareil center fielder”, “she's one girl in a million”, “the one and only Muhammad Ali”, “a peerless scholar”, “infamy unmatched in the Western world”, “wrote with unmatchable clarity”, “unrivaled mastery of her art”