Each of the Mercs has their own set of stats. The higher the stats, the stronger they are and the easier the game becomes. Mercs also have unique skills to assist them in battle. The stats are as follows.

List of Stats Effect in Autoplay Mode Effect in Survival Mode
Power Affects how much damage is dealt to the Infected Same as left
Fire Rate Affects the interval between attacks Same as left
Shot Pattern The pattern in which bullets fly Same as left
Shot Level Affects the amount and size of bullets Affects the amount, size, rate, and damage of bullets
Stamina Affects how long can a Merc fight (decreases over time) When it reaches 0, it’s game over
Skill A unique ability with powerful effects Same as left