Warhammer 40,000: Boltgun
21 Achievements
GOG
Rage Incarnate
Defeat a Helbrute
2.3%
How to unlock the Rage Incarnate achievement in Warhammer 40,000: Boltgun - Definitive Guide
A Helbrute is encountered in the 2nd level (Dread Ascent) before beating the level. I believe you have to defeat this enemy to complete the level, so pretty sure this is unmissable.
Unmissable, as lots of times you can't progress until all enemies are dead. In some of these sections there are Hellbrutes present. First appears on the second mission of the DLC.