Hmmm... Maybe no, villain for what??
Antagonist/villain is a strong call.
To be honest, if Andy were to introduce a villain it would probably be best to be outside of the main group of characters
Big(?) Spoiler:
Out of everyone who was in the picture, I'd say Herbert would probably be the best contender for an antagonist role in the story with all the flashback and mystery surrounding him. And as previously stated in Mark's storyline, Walter's mom did say Herbert was going out of his room more setting up an appearance or even maybe a start to his antagonistic role? Or I might just be looking into things too much lol.
But I could clearly see a story without the antagonist element introduced.