unrealistic colors
cartoon
realism 
3d
Poorly drawn
Bad anatomy
Ugly
Disfigured
Deformed
Distorted
Low quality
No shadows
No contrast
Unattractive
Childlike
Underage
NSFW (Not Safe for Work)
Imperfect
Facial features askew
Cropped limbs
Extra limbs
Incorrect limbs placement
Unprofessional
Messy lines
Blurry
Mismatched colors
Lacking detail
Inconsistent proportions
Jagged edges
Unfinished
Unpolished
Incoherent composition
Unrecognizable subjects
Awkward perspective
Unbalanced composition
Dull colors
Muddled textures
Inaccurate scale
Amateurish
Chaotic
Uninspired
Unengaging
Jarring colors
Inharmonious elements
Unpleasant subject matter
Unintentional abstraction
Unconvincing lighting
Repetitive elements
Cluttered
Uninteresting subject
Unrefined
Overly simplistic
Inadequate details
Unfinished background