Hunters are the heavy troops among the Swarm. Alliance doctrine advised that Hunters should only be engaged with overwhelming force and ideally only with powered armour units; even then the odds of survival were not great. Hunters seem to be a least partially resistant to projectile weapons either through their incredibly tough exoskeleton or their internal organs being capable of continuing to function even after catastrophic damage.
During the war Hunters, wherever possible, would be engaged with explosive rockets or more exotic weaponry in an attempt to kill or disable them as quickly as possible, as the damage they would do if they got among friendly troops almost always guaranteed a pyrrhic victory at best. Adding to their danger is the ability of a Hunter to employ some form of biological firearm launching shards of a bone like substance.
Perhaps the only advantage we have over the Hunters is mobility. They are slow and heavy creatures, so using the terrain against them are the best way to survive an encounter.