Most Terrifying Video Game Enemy?

[Dfskelleton]

These are my favorites here. They're all scary for different reasons:
Pyramid Head: The general idea of a man (?) with a giant rusty pyramid helmet grafted on to his head is creepy enough, but his state of invincibility and mysterious relations with the main character gives him another layer of menace. And, being chased down a long hospital hallway by him is also pretty intense and creepy.
The Grunt: The inability to defend yourself from the horrible mutants in Amnesia is scary enough, but this fear is multiplied by such horrific (in a good way) Monster design. Whoever designed this thing must either be a sick man or really really good at monster design. Seeing one of these running at me from down a hallway is truly horrifying. Well done, Frictional.
The Spider: LIMBO was already creepy enough, but when that spider shows up, everything goes to hell. It's practically a symbol of pure terror, and the fact that you can only see it's shadowy frame only makes it all the more terrifying.

 

[Jabberwock xeno]

Majora's mask.

No, not the boss, the game.

The whole damned, amazing game.

 

[cgmetallica1981]

Bloodsuckers from STALKER, the things that shoot poison head crabs in HL2, and vampires from Morrowind.
Those of you who say Creepers, are you 4? Oh no they destroy 4 blocks of your precious home.

 

[pyrosaw]

Poison Zombies creep me out. The noises....
I think it's safe to say all insects in Fallout games.

 

[ReservoirAngel]

Witches in Left4Dead.

The faint crying, growing louder...the swelling musical sting accompanying them...not to mention if you go near them or even LOOK at them with your flashlight on you set them off and they swiftly wreck your shit.

I can handle that game easy...but whenever I heard a witch's cry, I get hesitant to advance through outright FEAR of encountering it.

 

[LiquidGrape]

THAT pyro in Mass Effect 2.
You know the one I'm talking about.

Yes. Yes you did, you bastard. You broke me.

 

[KissofKetchup]

CREEPERS!!!!!!!!! God the scare the shit out of me whenever I hear that hiss

 

[kannibus]

The Hag from Thief Deadly Shadows, damn, but getting to those glyphs was scary as all hell!

 

[Uber Evil]

I'm surprised at how many people are scared of the headcrabs. I was absolutely fine during ravenholm. Also, the bloodsuckers don't scare me either.
OT: Err, I don't know. Puppets from Thief 3 have been mentioned. That whole level just terrified the fuck outta me. I don't remember any enemies that actually scared me. Oddly enough it seems that I don't really get scared by games.

 

[Kiefer13]

Well, there are two very definite contenders.

Spoiler: Number one

Poison headcrabs from Half-Life 2. Partly because of their horrifying death rattle, and partly because they look enough like spiders to trigger my arachnophobia. So yeah, fuck them. To be fair, I'm not a fan of arachnids or bugs of any kind in most games.

Spoiler: Number two

The titular Nemesis from Resident Evil 3: Nemesis. It very definitely lived up to its name, doggedly chasing you through the entire game. One of the only enemies in the series (up to 3, anyway, I've never really played much of the more recent ones) that could chase you through doors and into other rooms. The Nemesis was fast and it was relentless, and often the only warning of its arrival was the shattering of glass and a terrifying snarl of "STARS!"

 

[theSovietConnection]

While not an intended enemy in a game, I ran into flying Deathclaws (Flying. Who was the evil fucker who thought that up?) in Fallout 3 more times then I care to recall. As for my other choice, though, I don't think words can describe them well enough. While they no longer bring the same feeling of terror they once did, I still can't help but cringe every time I see these-

.

 

[beastly97]

the second thing that came to my were the cougars from red dead redemption because they can kill you in like to hits and if its a pack your'e doomed dude(the first thing was the bear from condemned 2, but then i realized what the question was)

 

[Nouw]

Aliens versus Predator 2 is a terrifying game with one of the most terrifying sci-fi monsters.

I gun down 'em basterds though.

It's a shame they apparently screwed the game up, guess Rebellion don't understand that no one has enough balls to actually hit an Alien.

Spoiler: Except these guys

 

[Kiefer13]

While not an intended enemy in a game, I ran into flying Deathclaws (Flying. Who was the evil fucker who thought that up?) in Fallout 3 more times then I care to recall. As for my other choice, though, I don't think words can describe them well enough. While they no longer bring the same feeling of terror they once did, I still can't help but cringe every time I see these-

.

Indeed. Zubat are one of those enemies that while not much of a threat individually, soon begin to inspire a feeling of dread at their appearance, just because there are so goddamned [http://tvtropes.org/pmwiki/pmwiki.php/Main/GoddamnedBats] many of them.

Spoiler: Rather like these fellows...

 

[Chimpzy_v1legacy]

ReDeads, mostly because their sole purpose in life seems to be invading your personal space.

 

[Zantos]

The Necromorphs from dead space. I didn't think they were bad til i took a break to get a drink, heard something rustle in the cellar and shit sticks while running to my room to lock myself in like a little girl.

 

[TheColdHeart]

The necromorphs in Dead Space, the first time you blow it's head off and it keeps coming at you, so you blast it's legs off and the fucker keeps crawling at you! And they can seem to come from anywhere made them absolutely terrifying.

At least Isaac had some hefty ass-kicking boots on.

 

[Brazilianpeanutwar]

GAHDAMN SPLOICERS!

 

[PAGEToap44]

uuuuuuuuungh
grrrrrrrrugh

Most recently this. Them or Creepers, they take such pleasure in destroying my beautiful creations.
Other scary things include most of the monsters from Metro 2033, the Flood from Halo (when I was a kid, seriously, Flood levels in Halo 2; freaky shit.) Also most of the enemies from Silent Hill: Homecoming. It may have been a shit game but it's the oly Silent Hill game I've played and I found it fucking scary.
Another one that probably doesn't count for me are the zombie things from Amnesia: Dark Descent, because I've never played it, just watched other people play it.