The Collaborative International Dictionary of English v.0.48:

Unflattering \Unflattering\
   See flattering.

WordNet (r) 3.0 (2006):

unflattering
    adj 1: showing or representing unfavorably; "an unflattering
           portrait"; "an uncomplimentary dress" [syn:
           unflattering, uncomplimentary] [ant: flattering]

Moby Thesaurus II by Grady Ward, 1.0:

81 Moby Thesaurus words for "unflattering":
   authentic, bona fide, candid, card-carrying, dinkum,
   following the letter, genuine, good, guileless, harsh, honest,
   honest-to-God, inartificial, insulting, lawful, legitimate,
   lifelike, literal, natural, naturalistic, original, pure, real,
   realistic, rightful, simon-pure, simple, sincere, stark, sterling,
   sure-enough, true to life, true to nature, true to reality,
   unadulterated, unaffected, unassumed, unassuming, unbeguileful,
   unbeguiling, uncalculating, uncolored, uncomplimentary,
   unconcocted, uncopied, uncounterfeited, undeceitful, undeceiving,
   undeceptive, undesigning, undisguised, undisguising, undissembling,
   undissimulated, undissimulating, undistorted, unexaggerated,
   unfabricated, unfanciful, unfavorable, unfeigned, unfeigning,
   unfictitious, unimagined, unimitated, uninvented, unpretended,
   unpretending, unqualified, unromantic, unsimulated, unspecious,
   unsympathetic, unsynthetic, untrimmed, unvarnished, verbal,
   verbatim, veridical, verisimilar, word-for-word