Poll: Who was Dexter's Creepiest Adversary?

Showtime is now showing all eight seasons of their series, and NuvoTV is also airing episodes every Sunday afternoon and Monday evening. Whether you're watching the groundbreaking show for the first time or just reminiscing, which of Dexter's adversaries embodied the most hair-raising blend of scary and strange? SPOILER ALERT: Do not continue if you have not seen most of each of the following seasons but plan to: Seasons 2, 3, 5, and 8. Discuss here