The Collaborative International Dictionary of English v.0.48:

Chiefest \Chief"est\, a. [Superl. of Chief.]
   First or foremost; chief; principal. [Archaic] "Our chiefest
   courtier." --Shak.
   [1913 Webster]

         The chiefest among ten thousand.         --Canticles v.
                                                  10.
   [1913 Webster]