until now is the Cyborg Midwives.really their speech pattern is scary as hell and when you are on deck 3 and everything is closed corridor their voices seem to be coming from everywhere.

I haven't met the Midwives yet. Although Hybrids are probably technically scarier, the monkeys freak me out more. >.>

I'd say the helper robots that are below decks are the worst for me. (I forget what they are called; haven't played SS2 in a while). They look slightly skeletal or out of proportion, and have that persistent whirring noise as they walk. And, well, they tend to catch you when you are low on anti-bot bullets.

The spiders, especially later on when they are harder to see.

No contest, the cyborg midwife is the most terrifying enemy. Their background, their purpose, dialog, the clanking, their voice...yeah, just horrifying.

The cyborg midwives are the creepiest and with the most unsettling backstories but in terms of gameplay the protocol droids are just awful. Maybe the only enemy in the game you can't even stand right next to without potentially getting yourself killed, let alone while melee attacking them. And they're most plentiful in the early portions in the game in the area with the tightest spaces and where your ammo is most limited. Ugh. Actually any of the mechanic enemies, from the turrets, security bots, and the most dreaded enemy of all, the SECURITY CAMERAS, are all roughly equally unpleasant to encounter. I also hate the spiders for all the anti-toxins you can waste while trying to fight them. The swarms are pretty bothersome too.

The rumblers aren't too bad when you're fighting them head-on but the sounds of their presence are pretty scary, especially if you don't know what you're getting into (also pretty creepy-looking themselves, just give a good look at their shoulders when you get the chance...).

Probably the Midwives. They're difficult, and they're incredibly sick and twisted.

I am not fond of C3PO's evil doppelgangers.

Regular Hybrids, they just seem so tragic...

The monkeys.

Cyborg midwives give me the creeps, but I also dislike it when an egg hatches in my vicinity.^^

So far the monkeys when they are not visible >_> I hate their voice.
Most annoying so far is the shotgun hybrid. Looking forward to meet the Cyborg midwives

I just met my first Midwife! Creepy! The encounter consisted of me dashing past her into an elevator because I had 7 HP. The savior of Earth, ladies and gents!

Okay, yeah, after some more encounters, definitely Midwives. I'm going to go hide in the corner now.

To me, the midwives will always be the worst. It's just something about them...