The Zombie Hunter is first encountered as an NPC around Recoil Ridge while the player attempts to kill The Infected troops attacking on the World Map. He later shows Ramsey and Lt Morgan the location of the infected. The unit was subsequently released as a limited-time unit for 60 during the 4th Boss Strike.
The Zombie Hunter is the nemesis of the Infected as the Z.Hunter's first and second attack will always crit on zombies, dealing extremely high damage. This unit was very effective during the Infected Boss Strike and through the Halloween missions with infected troops. While leveling to Rank 6 can take an hour, the Rank 7 takes a lot more time, even days. During the 4th Boss Strike, it was recommended to place this unit on the front row because of its high Dodge, it could easily dodge the attacks but on higher enemy levels, it was preferred to place this unit on the second row since the only effective attack is the shotgun attack.
The attack name for the Boomstick may be a reference to the action-comedy movie Zombieland, in which the main character emphasizes "double tapping" zombies to make sure they stay down.
Actually, it's likely a reference to the "Evil Dead" series where the main character "Ash" uses a sawn-off double barrel that he calls his "Boomstick" and a chainsaw