polar opposite

plural polar opposites

1. The complete opposite, opposite in every way.

   Rusticity and Urbanity are polar opposites—and there lie between many million modes of Manners.

   1832 June, Allan Cunningham, "The Maid of Elvar," Blackwoods Magazine, p. 998 (Google preview)

   2 more examples

   Buddhism, which regards all existence as no more than illusion, and the philosophy of existence, which regards existence as real behind the illusion of becoming, are, so to speak, polar opposites.

   1960, Hellmut Wilhelm, Richard Wilhelm, Understanding the I Ching, →ISBN, page 154

   [S]he is the prim, androgynous-sounding twin. . . . Her polar opposite, Abigail is the plump, lusty twin.

   2003 September 25, Janet Maslin, “Books of the Times: A Family's Fatuousness”, in New York Times, retrieved 13 Dec 2015