|“||Now take Sir Francis Drake, the Spanish all despise him, but to the British he's a hero and they idolize him. It's how you look at buccaneers that makes them bad or good, and I see us as members of a noble brotherhood!||„|
|~ Long John Silver in Muppet Treasure Island.|
The main characteristic of a person or group in the "Grey Zone" is that some will consider them dangerous, criminal or "evil" while others may see them as good, scapegoats, or fighting for the right thing (even if their methods are wrong). These villains try to act evil, but they have some positive and redeeming qualities.
Some characters in fiction are deliberately designed to be in the Grey Zone and it is up to the reader or viewer to decide if they are a "hero" or a "villain"; as a result, each reader or viewer will probably have a different view of him/her (V is a classic example of such a character, so is Ozymandias).
Villains that are Pure Evil can never be in this category for they remain bad whereas it is unknown if Grey Zones are bad or good. Also, this is not for villains that are simply remorseful or relatable: it must be debatable what side they are on; if they act evil and/or know they are evil, they do not apply here.