"You sick son of a bi***!"
"A common condemnation of someone else being a pervert"

These villains tend to possess abnormal, "sick" desires, usually of a twisted and/or (usually) sexual nature. Though being a pervert is not entirely evil, especially if it's at a relatively harmless level (such as "reading" pornography), people in this category take it way too far, with rapists, zoophiles, pedophiles, necrophiliacs, and incestuous being examples of what qualifies as a villain.