Run or shoot?... RUN OR SHOOT?!
~ Louis
Why can't that thing be on our side?
~ Rochelle

Tank is the primary antagonist in Left 4 Dead and Left 4 Dead 2. It is the biggest threat to the Survivors and are a rare type of boss/special zombie.

The Tank is always male who has experienced the most physical mutation of all of the infected. Its most notable trait is its increased muscle mass. It can be assumed that its bones have grown in strength too otherwise the Tank's skeleton would have collapsed under its own weight. Despit the Tank's incredible muscle mass, it is surprisingly fast and agile, able to keep up with a Survivor at full health. Its muscular growth is most obvious in its arms and upper body, and is less pronounced in its waist, hips, and legs. Though its legs are capable of supporting its static weight (such as when it mounts onto its legs to throw a giant rock), its disproportionate anatomy forces it to knuckle-walk like a gorilla, resulting in its wrists becoming swollen. The Tank's body is covered in scars from previous fights, with a noticeable large sore on its left pectoral. The Tank's jaw, at first glance, appears to be missing, but upon closer inspection, it is shown to be enveloped in its neck muscles.

The Tank also appears to have suffered heavy brain damage or a rabies-like cerebral infection, causing it to be in a constant rage. When it has found an unlucky target, nothing short of death will stop it; bullets have no affect unless all focus their fire on the abomination, fire only slows him down, and pipe bombs and car alarms do not distract him (although in the intro scene, it was a car alarm that alerted the Tank, as well as a horde of other infected). The Tank will even break through doors, knock away obstacles, uch as cars, and knock away or crush any infected in its way just to get to the unlucky Survivor it has chosen as a victim.

The Tanks in the first Left 4 Dead game will attack one Survivor at a time, attacking him/her until the Survivor is dead, then it will attack a second victim. While this is unfortunate for the victim, it gives team mates an opportunity to strike the infected. Tanks in the first volume will be spawned once at a time and at fairly predictable times and location, often uttering a growl and an arm flapping movement that gives away their position. Since Tanks lack motor agility, a skilled Survivor can dodge a Tank's direct attacks. A Tank is especially dangerous if one catches the Survivors in a tight chokehole, such as a small room.

The Tank recieves a variation skin in The Sacrifice at a specific location in The Docks. This Tank is bald, has jeen shorts, surgical scars, missing front teeth, no shoes, a Marine Corps tattoo on its chest, and what appears to be leather restraints on its wrists. Its hands and forearms are covered in fesh blood.