The first time I recall being terrified by zombies it was a horror flick that had something to do with Voodoo. Once upon a time, zombies fell clearly in the realm of supernatural horror. 
They were the dead, crawling up out of the grave in search of tasty brains. Now days they are more often the afflicted, dead or otherwise, a result of a virus or bio-weapons or science gone wrong. Which is scarier? I think they are both scary in their own way.
Horror Zombies
The original horror zombies can usually be attributed to the supernatural or occult religions. In that Voodoo movie I mentioned, the zombies were just people who’d been drugged, then buried alive. Victims, really. Being buried alive is pretty scary. But if you want a chilling look at zombies as the dead brought back to life by blood and magic check out Those Who Seek Forgiveness by Laurell K Hamilton, rereleased in her Strange Candy collection of short stories. This was the story that introduced Anita Blake and Animators Inc of the Anita Blake Vampire Hunter novels. This story takes a deep look at death, grief, and loss.
SciFi Zombies
One of the most successful zombie franchises (games, movies, books) has been Resident Evil and the zombies created by the Umbrella Corporation’s mutated T-Virus. In this, as in many zombie stories, the scariness is twofold. There is the fear of being overwhelmed by large numbers of shambling witless dead and eaten alive and then there is the fear of becoming a zombie. In The Walking Dead, AMC’s recent TV hit, based on the comic series, the dead are again scary because of their numbers. One on one, the characters will defeat the zombies, but stumbling into a large group—or attracting one—is deadly. If you ever find yourself in this type of zombie uprising, keep in mind the tips in my post on Ten Things I’ve Learned from the Walking Dead. These not so smart zombies are also the type most often found in zombie comedies like Shaun of the Dead.
Scariest Zombies of All
My personal favorites are the zombies in the We’re Alive audio drama. These zombies are far from the shambling brain eaters. They are strong and fast with heightened senses. Some are smart enough to plan traps and organize others. The worst of all possible worlds and very scary.
So do you prefer supernatural or SciFi? What do you think are the scariest Zombies and why?
Smart Girls love SciFi 