The Collaborative International Dictionary of English v.0.48:

Soulless \Soul"less\, a.
   Being without a soul, or without greatness or nobleness of
   mind; mean; spiritless.
   [1913 Webster]

         Slave, souless villain, dog!             --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

soulless
    adj 1: lacking sensitivity or the capacity for deep feeling

Moby Thesaurus II by Grady Ward, 1.0:

65 Moby Thesaurus words for "soulless":
   abiotic, affectless, anesthetized, arctic, autistic, azoic, blunt,
   catatonic, chill, chilly, cold, cold as charity, cold-blooded,
   coldhearted, cool, dispassionate, drugged, dull, dumb,
   emotionally dead, emotionless, exanimate, frigid, frosted, frosty,
   frozen, heartless, icy, immovable, impassible, impassive,
   inanimate, inanimated, inert, inexcitable, insensate, insensible,
   insentient, insusceptible, lifeless, mute, nonconscious,
   nonemotional, nonliving, objective, obtuse, out of touch,
   passionless, self-absorbed, senseless, spiritless, unaffectionate,
   unanimated, unconscious, unemotional, unfeeling, unimpassioned,
   unimpressionable, unloving, unpassionate, unresponding,
   unresponsive, unsusceptible, unsympathetic, untouchable