When a character has been possessed often enough to be able to tell you how the thing possessing him was feeling, while the other main characters on the show don’t even understand why possession is bad, there’s a problem.
Am I the one who noticed that? When Sam and Dean come to take The First Blade, helllhound appeared, yeah? But Dean looked STRAIGHT to it, it looked that he can actually SEE a hound of hell. It’s terrifying.