"Unflattering comments" refers to negative or critical remarks about someone's appearance, behavior, or qualities that are not complimentary or kind. Full definition
I read another review of this device, where the author give very unflattering comments about Blackberry Torch, cited the case when the phone blew up in the hands of the user. (newgadget.org)
«You may come to read unflattering comments by colleagues, and they may go into your personnel file. (inc.com)
Swords are unsheathed and unflattering comments fill the air. (courant.com)