Psychopathy, loosely defined, is a combination of cold-heartedness and violence. The most extreme psychopaths may kill without remorse, mutilating victims with as much emotion as you or I might brush our teeth.

This is known as "classic" or "idiopathic" psychopathy, but sometimes the disorder is more covert, as with some manipulative smooth talkers who aren't necessarily violent.

In 2014, Belgian psychiatry professor Samuel Leistedt wanted to find out which movie characters embodied psychopathic traits best.

Leistedt called on 10 of his friends to help him watch 400 movies over the course of three years. The films spanned nearly a century, from 1915 to 2010. When the team finished watching all the films, they'd found 126 psychopathic characters.

Here's a breakdown of their findings.