Stalkers – Borderlands 2
The easiest way to make a video game enemy incredibly annoying is to give it the ability to become invisible. And that’s exactly what Stalkers do: When they smell nearby prey, they cloak themselves and begin sneaking up on the unlucky Vault Hunter. There are several different kinds of Stalkers, too – some have a ranged attack and others leap straight in to engage you in melee.
Point is, they can be invisible. That’s super annoying.