Dress the villain in black. From Venom, Spiderman's nemesis to Black Adam, one of Captain Marvel's enemies, comic book and film villains look best swathed in black. The costume material can be leather, spandex, silk or latex, but as long as it's black, the bad guy (or girl) persona shines through. Add a cape and black hat for a Western movie villain.
Give the villain an ominous prop. A villain yields foreboding accessories like chains, spikes, fire, flares, a torch or a chainsaw. With enough imagination, you can turn just about any household item into a menacing villain's accessory.
Create a functional but come-hither costume for a female villain. Bright, tight spandex or leather costumes befit a female villain like Catwoman or Harley Quinn. Add a whip, handcuffs or other sexy gear to complete the look.
Add evil, glowing eyes. The eyes are the window to the soul, so use cat eye contact lenses to instill a glowing, evil or just plain intense look in your villain's eyes.
Craft scars or markings on the face or body. Create a slash across the face, a burn or a menacing tattoo to give a villain an intimidating look and embellish the costume. Also consider a dark or bloody mask to cover any facial deformities.