Source : Webster's Revised Unabridged Dictionary (1913)

Iniquitously \In*iq"ui*tous*ly\, adv.
   In an iniquitous manner; unjustly; wickedly.

Source : WordNet®

iniquitously
     adv : in an iniquitous manner; "they really believed that the
           treaty of Versailles was iniquitously injust"