From Halopedia, the Halo wiki
Brute grenadiers are madmen and savages who are too unstable and crude to advance in the Banished hierarchy. With few other options to seek glory, they turned to Voridus, who offered a place in the vanguard of his pack for any willing to test his latest inventions. While many achieved the glory they desired their bodies began to rot from the inside out from exposure to the infusion they abuse. Grenadiers are typically equipped with iatrochemically-enhanced armor and grenade launchers that can be overcharged by infusion.
Awakening The Nightmare
Jiralhanae Grenadiers are exclusive to Voridus and can be built at Raid Camps in place of Suicide Unggoy, and are also available in the mission The Archive through the teleporters. Grenadiers do well against infantry, but poorly against vehicles, aircraft, and structures. Once the Hard-Target Detonators upgrade is purchased, Grenadiers will perform okay against aircraft. Once the Infused Grenades upgrade is purchased, Grenadiers will perform okay against vehicles. In Blitz, Scarred Grenadiers replace the standard Grenadier unit, and cost 50 energy.
List of appearances