Amata Lirein
...and NPCs using a totally overpowered gun in supposedly low-level threat areas that two-shot you even if you had your suit's shields online. (AFAIK that was supposed to have been removed even during the alpha...)
That OP gun is Manticore Executor. They use aim bot, so if you not change your movement constantly you are doomed. The weapon will kill any NPC with 3 shots even at grade 1.