Hive Guard
As their name suggests, the Hive Guard or "Interloper" are a sub-strain of Warriors most commonly found within hives acting as their wardens and perhaps as a response to the since cherished SEAF pastime of throwing a grenade down a bughole, using their now enlarged heads to block up said holes. Effectively a mutated Warrior-class Terminid, its head and front legs now covered in especially dense layers of highly resistant chitin capable of completely resisting conventional small arms fire much to our dismay. Unfortunately for us they are smart enough to exploit their armour by curling up into a defensive posture the moment they feel threatened. The Ministry of Defense and I myself recommend bringing some armour-piercing ammo and focusing fire onto their ugly faces for the best results.
While well protected in their curled up posture, SEAF veterans have identified certain exposed weakpoints such as the leg joints and claws, while nowhere as efficient as simply puncturing its massive head, it will do in a pinch with lower calibre weapons
Despite being practically immune to small-arms fire, their carapace is still vulnerable to explosive ordinance such as grenades which are capable of even shattering said carapaces, use them when they are huddled up for maximum effect.