What is the scariest version of the undead that have been created in fiction?

[Mahorfeus]

The demilich.

No, seriously, screw those things. They are irritable like rattlesnakes, except when you piss these things off, they can curse you and devour your soul. Not to mention that they are nigh indestructible.

God save you if it is awakened, because that means it retains its intellect and all the spells it had as a lich.

 

[Reaper195]

Running zombies. Fuck all kinds of that.

This, its pretty common to see that once a zombie has latched onto you, its game over, but in most zombie stories, they are slow and easy to get away from, but having a horde of the fucking things running at you by the hundreds is just terrifying and the ones in Left 4 Dead look creepy as hell.

Did you see World War Z? Incredibly accurate what would happen with hundred, thousands of ombies running at your face. It'd be like a fuckin' wave of flesh just rolling towards you.

 

[Vicarious Reality]

Does this count? Technically the people it takes would be dead right?
Many zombie stories have the same premise, perhaps that is only a depreciation of the concept of the draugr

 

[SNCommand]

Definitely the Necromorphs, just because they affect everything

You die? You turn into one of them

You lose your arm? It turns into one of them

Your dead cells? Turns into one of them

You eat them? You turn into one of them

 

[AetherWolf]

I've started watching The Strain, which premiered fairly recently, and I think its zombie-vampire... things... are among the most unnerving I've come across yet. Guillermo del Toro is a master of creating great monsters, so it's no surprise.

Oddly, the one thing that disturbs me the most about them isn't the worms or the tongue-tentacles, but that the virus causes the genitals to merge into a cloaca. I don't even know, man.