General:

low quality
noisy
deformed
unrealistic
text
watermark
out of frame
underexposed
overexposed
low contrast
blurry
Anatomy & Composition:

extra limbs
missing limbs
fused fingers
disconnected limbs
disproportioned
bad anatomy
ugly
disfigured
poorly drawn
Style Specific:

simple background
plain background
cartoon
painting
grayscale
monochrome
