Good. Bad. I'm the guy with the gun.
~ Ash Williams, responding to his doppelganger
You might look like me, but I know you're just a fake.
~ Shadow to a Shadow Android
Tink: Two fairies born of the same laugh. So... That means...
Peri: You're my...
Tink & Peri: So.. We're... SISTERS!!!
~ Tinker Bell and Periwinkle

A good twin or a good clone can be an attempt at creating a good version of a villain by science or magic - It can also be an alternative version of a villain from a twisted reality / timeline: On some occasions, it can be a literal twin of both the identical varieties. They can be also Good Counterparts meaning they share some similarities to the villains and their background.