The Mercenaries are survivors of the Fortune City outbreak, armed with Merc Assault Rifles. There are three different groups of mercenaries, including those dressed in orange jumpsuits with bulletproof vests and hardhats, goons in tuxedos similar to the way Tyrone King dresses, and soldiers in black and blue gear in the Underground Lab. Thirty-six in all, they are employed by Phenotrans, the Zombrex manufacturers, to harvest Queen Wasps from zombies throughout the city, as well as to help Tyrone King steal money and valuables from the abandoned casinos.
While in groups, their gunfire can be troubling. Using cover to get close is especially important if you haven't learned dodge roll yet.
They are easy to dispatch one on one. Just dodge roll away from their shots until you can get close enough to attack. Remember that dodge rolling causes you to drop heavy weapons!
Use strong weapons or jump attack with the Defiler as it is extremely effective.
Two swings with the Spiked Bat is enough assuming Chuck has even a couple points in Attack, and a moderately leveled Chuck can take them out with one swipe of Knife Gloves. One blow from a good weapon will knock them down - hit them again as they are getting up to finish them off.
If Chuck is low on health, try to catch them as they are reloading.
Have survivors help you while fighting. Arguably, the best survivors to help you are the band members of Angel Lust as they can be recruited during the case Run for the Money.