Toxin rebel

Dr. Thrax's Toxin Rebels eschewed the usual assault rifle in favour of a toxin-spraying weapon with backpack toxin-tank (similar to a flamethrower), and were known as Toxin Rebels. This made them effective at eliminating infantry, even ones garrisened in buildings and bunkers.

Counters
Anti infantry vehicles such as the Gattling Tank and aircrafts could easily mow down Toxin Rebels.