I said Tak because he freaked me out the most. An animalistic entity that only wants to hurt and can command animals? Although, R.F. in his many incarnations did the same thing, but for some reason Tak was scarier. I loved the shit he pulled in The Stand, just the crazy shit. But I guess the fact that he could be tricked
Spoiler:
(when Dana, I think her name is, jumps out the window and thwarts him)
and has vaguely human tendencies makes him less scary.

Although Norman Daniels scared me too, simply because the very idea that a man could be so abusive and scary frightens me.