Use nonpareil to describe someone or something that is beyond compare, an absolute model of perfection of a particular thing. Jane Austen was a writer nonpareil, and James Bond a spy nonpareil.
Coming from the medieval French words non, meaning "not," and pareil, meaning "equal," so quite literally it means "not equal" or "unequaled." Like a lot of fancy French terms adopted by the English language (e.g., "bons mots," "eminence gris"), the use of nonpareil is generally restricted to written form. Use with caution.