scariest enemy/ally in video games?

Verdugo-Resident Evil 4. 

anyone remember that scary as fuck zombie from REmake? i think it was called Crimson Head. first time I saw that i almost shit myself 

Pyramid Head: Silent Hill 2.

Video games aren't scary.

Depends, as my older brother had an affinity for brutal games when he was younger as any teenager has, I was exposed to high levels of sacariness right from the time I stated playing my first video games during elementary school. So even Doom, Quake, hell even Half Life gave me a good scare. Blood 2: The Chosen had those little beasts which jumped right into your face and I didn't know how to kill them which was horrible to say the least. Another intense moment was right at the beginning of Breakdown (Xbox game) where there are some enemys that you just cannot hurt but which still rush after you.  
Even today I prefer avoiding scary games like Condemned as I get no pleasure out of such games.  
But if I have to narrow it down to just one scary opponent I think I should go with Beruga from the 1996 SNES game Terranigma - this guy just gave me the creeps, he had wires and stuff sticking out under his lab coat. He also had cultist worshippers how wore robes and where absolutly fanatic about his ways. Though it's not really scary anymore it gave me a good chill when I was ten :-) 

nemisis from resi 3 espically anytime that he chased you

Sitting here for like 10 minutes I can't think of any time in a game I have been super scared of an enemy or an ally. At least not the kind of "scared" I assume we are talking about here. A few games though have made my heart skip a beat because of an enemy, but I wasn't "scared" of them. 
 
The most recent example of this happened today, while playing Fallout 3 I went into Jericho's house in Megaton to steal his Chinese Sword. The second I opened the door to exit I saw his giant angry face taking up my screen saying one of his angry-I-may-snap-and-kill-you remarks. I shouted out loud to say the least.

" anyone remember that scary as fuck zombie from REmake? i think it was called Crimson Head. first time I saw that i almost shit myself  "

I always dread fighting Ridley in Super Metroid, because he ends my speed runs half of the time.

Pac-Man's enemies.......

NEMESIS!

" Pyramid Head: Silent Hill 2. "

The red kimono girl in Project Zero II(Fatal Frame in the States).
 
"What's with that creepy, knocking sound from below the floor? Let's check it outOH FUCK A CREEPY LITTLE GIRL NOW SHE'S GONE WHERE DID SHE GO WHERE DID SHE GO OH FUCK SHE'S BEHIND ME NOW I KILLED HER, phew" 
 
"Now I'm going to open this closetOH SHIT THERE SHE IS AGAIN WHAT THE FUCK I KILLED HER A COUPLE OF MINUTES AGO NOW THE SCREEN WENT BLACK WHAT'S HAPPENING, NOW I CAN SEE AGAIN, TAKE THA, phew." 
 
"I've killed that girl twice, so she's probably not coming back. It's probably safe to open this closetOH GOD THERE SHE IS AGAIN WHAT IS WRONG WITH THIS CHICK WHY CAN'T SHE JUST STAY DEAD FOR CHRIST'S SAKE NOW I DEFEATED HER AGAIN, phew". 
 
 I hate her.

The little girl from F.E.A.R. actually.. just about anything from that game.  I just about fell out of my chair on multiple occasions.