Second to none = Ne plus ultra

ne plus ultra \nay-plus-UL-truh\ noun *1 : the highest point capable of being attained : acme 2 : the most profound degree of a quality or state
Example sentence: "Some believe that a string quartet performance is the ne plus ultra of chamber music." (Eileen Soskin, The Baltimore Sun, April 29, 2005)
Did you know? It's the height, the zenith, the ultimate, the crown, the pinnacle. It's the peak, the summit, the crest, the high-water mark. All these expressions, of course, mean "the highest point attainable." But "ne plus ultra" may top them all when it comes to expressing in a sophisticated way that something is the pink of perfection. It is said that the term's predecessor, "non plus ultra," was inscribed on the Pillars of Hercules at the Strait of Gibraltar, which marked the western end of the classical world. The phrase served as a warning: "(Let there) not (be) more (sailing) beyond." The New Latin version "ne plus ultra," meaning "(go) no more beyond," found its way into English in the 1630s.