User blog comment:Noctosphere/Who do you think should be the Big Bad of S12/@comment-24831339-20170530212846

I think the main antagonists are Lucifer and Arthur Ketch

Arthur Ketch was getting orders from Dr. Hess but he was the driving antagonist (representative of the BMOL more so than Dr. Hess) all season long against the brothers. His link with Mary made more of a personal big bad for the brothers than Dr. Hess. Even if he was "the heavy" or "the dragon" in tropes terms, he was the direct big bad Sam and Dean had to fight.

Lucifer was stirring trouble even since episode 1 of season 12 even if he was unseen and had no plan. He got his focus back with the news of his son coming. He was firmly confirmed as the main antagonist and final boss of the season.

I think the secondary antagonists are Toni Bevell, Dagon and Dr. Hess