Draw the eye shape with sharp, narrow angles
Make the upper eyelid heavy and drooping
Add a thin, intense iris
Shrink the pupil to a small dark dot
Surround the eye with deep shadows
Add thick, jagged eyelashes
Tilt the eyes slightly inward
Use uneven lines for a tense look
Darken the corners of the eyes
Add wrinkles or creases around the eyelids
Make the whites of the eyes dull or gray
Add red veins across the sclera
Leave harsh highlights for a cold stare
Sketch under-eye shadows
Emphasize asymmetry between both eyes