resident evils if they're different kinds of evil, residents evil if theyr all the same kind of evil as residents
i see a doctors for my teeth, it's a son and father practice, and it always amuses me when i read their sign!
Resident Evils: Having lots of skeletons in your closet.
Residents Evil: Having lots of skeletons in a closet.
"resident evil", being a mass noun, cannot be pluralised without a counter, so the plural is two loaves of resident evil.