I love the headcrabs, i always tried to bat them away with the crowbar as they jumped at me, made it more fun!
Hmm... Pinky Demon (Doom 2016) Because I'm an idiot, I insisted on playing through on Nightmare difficulty on my only playthrough. The Pinky Demon was the most annoying enemy as it was damn fast and could pretty much kill you outright with one hit. Weird jumpy dart firing enemies (Half Life 2 Episode 2) Quick, tough, and fired darts with a delayed damage effect. Loved running the bastards over when you got the chance to. Torque Bow Enemies (Gears of War) The moment when you get hit by one of these and have a few milliseconds left to contemplate things before you're blown into gibs. Stalker (Horizon Zero Dawn) Aside from having cloaking, has a one hit kill melee attack regardless of level, which makes it more dangerous than any other enemy in the game. Khaak Cluster (X series) These bastards are the only faction to have hitscan weapons in the X series of games. In low numbers, you can manage them, but en-masse, the large amount of autohit low damage weapons will mercilessly hammer you into oblivion, regardless of how much dodging, diving, ducking and dodging you do.
Lambent Wretches (Gears) Basically neuter both shotgun and chainsaw, making Horde even harder than it already is or has to be. I'll also throw in... ...Queen Myrrah (Gears 3) She can be the flag bearer for any enemy in any game that requires multiple (commonly three) identical attempts at multiple (again, often three) stages of boss takedown. Just becomes a chore, especially on subsequent playthroughs at harder difficulties. EDIT: I am now adding the multiple waves of striders/hunters at the end of HL2: Ep 2. They take the Queen Myrrah annoyance up to 13.
