Definition of a Villain

I'm making this, because I was reading some articles that I feel don't fit the qualification for being a villain. For example, there's a majority of antagonists from the SuperMarioLogan video series who aren't villainous; for instance, there's the Squirrel from "Junior Gets Rabies" who, while an antagonist, doesn't do anything villainous other than bite Junior, who foolishly tried to pet it. If anything, Junior should stay, because he had committed a few heinous actions, namely murder.