Eh, Pinkie is far worse. At least with Slenderman you know what you are dealing with. Pinkie? She can go from this
[link] to this
[link] and do crap like this
[link]. With Slenderman you know what to expect and the worst thing he can do is kill you. Pinkie on the other hand doesn't want you to die.....quickly. She'll try to keep you alive as long as she possibly can as she tortures you. Hours and hours of constant and unimaginable pain. Also, Slenderman is more of an omen than a killer. He appears in the face of impending doom or death.