1. Randall Flagg (The Stand)
There are many reasons why Randall Flagg is the greatest Stephen King villain but the most overarching one is that he crops up in numerous novels. He's mainly known for his villainy in The Stand where he achieves a cult-like following who he controls and punishes for disobeying his fascistic regime. But he's also cropped up The Eyes Of The Dragon, arguably Hearts In Atlantis and then The Dark Tower series. Each time Flagg has a thirst for power and destruction, making him a deservedly recurring bad guy.