The Walking Dead, Vol. 23: Whispers Into Screams

The slow burn mystery of the Whisperers is really what makes this, and the surrounding volumes, shine. They're not as open about their motivations as Negan or the Governor or the Hunters, they're not seen as much as they hide within the dead. They use gorilla tactics, they're not terribly showy villains, which makes them a far more unique threat than just another human group trying to take down Rick and the other groups. Though I think Lydia was done far better in the show, that's one of the few times I'll say something like that.