As much as I want to say no, I can't. Typically villains are complex and have backstories, there are always exceptions, I just haven't found any yet.

Yes, it's taken me a LONG time to figure out how to answer this but YES! How did I come to this conclusion (I know nobody asked or wants to know but I'm gonna tell anyway)? With Peter Pan from Once Upon A Time! I even made a poll for it and here is my comment explaining why!

"A Gary Stu (male version of the term Mary Sue) is usually a character with little to no flaws, who doesn't really struggle, things come easily to them, and a lot of times is a self insert for the creator of the character. I once saw a poll asking is a villain could be a Mary Sue/Gary Stu and I wasn't sure how to answer, until now. Pan is definitely a Gary Stu villain. Why? Because, how many times did he ever appear to have lost and seemed genuinely stressed or angered by it. I mean, even Rumple, who could FREAKING SEE THE FUTURE, didn't always know what would happen and would get angered when things didn't go his way. Yes, I know villains are meant to cause conflict for the heroes but it goes both ways. Regina was stressed about Emma being in Storybrooke because she would break the curse (along with being concerned about taking Henry away). It encourages the villain to strive to work harder to achieve their evil goals and just when it seemed like the heroes one, the villains cleverly won in that moment because they tried to make sure that they wouldn't win by thinking HARD! We've seen this with ALL of the other villains EXCEPT PAN! What fun is it if it looks like the hero will never win and that the villain doesn't have to struggle. I respect villains who see a struggle, get stressed about it (usually showing it in a badass way), and thinking cleverly of a way to win. With Pan, he seems to know everything and doesn't take anything too seriously, even when it looks like he's lost. You know why? Because, he's a Gary Stu villain that's just so badass and evil that he pulls something out of his ass to defeat his enemy. I mean, he defeated Rumpelstiltskin of ALL PEOPLE! THE FREAKING DARK ONE WHO IS THE MOST POWERFUL BEING EVER! Pan maybe powerful but NOT THAT POWERFUL! He gets pandoras box VERY easily like it was nothing with no struggle, he escaped being trapped in pandoras box when he appeared to be defeated, he managed to be immune to the magic object that would strip him of magic, has NO weaknesses (even without love, Rumple still had a weakness, his dagger), and even when Rumple says he's finally willing to die in order to kill him he just smiles like "whatever." He's aware of what a Gary Stu villain he is and thinks he can escape death when he's told he's going to die. WHAT THE HELL? NO VILLAIN IS THAT UNBEATABLE! Not only is Pan a despicable and unlikable character, but this just makes him a terrible villain as well."

I am not sure why it fucking matters if a villain is one or not.

^ Wow! That comment makes you sound angry because of your current icon of a VERY angry character lol. I don't know why I just said that but OH WELL!