Screepo= a Scary + Creepy person. A synonym/another way to call someone "creepy" but with the added dimension of being "scary" - a.k.a dangerous and potentially harmful.
It's usually a male who stares at women and makes them feel uncomfortable in public places, such as a bar or club; in addition, he also maintains a persona of a serial killer or something of the sort. It is not someone girls can just say "Eww creepy", but they have to physically remove themselves from the presence of the Screepo because of the element of danger associated with him.
Two girls at a bar
Girl 1: Eww that guy gives me the creeps
Girl 2: That's not just a creepy guy, that's a screepo. Let's bounce.