Left 2 Die
The stank appears in the map Left 2 Die as a zerg NPC unit. It has a boss bar when appears. Every once in a while it will do an extra powerful attack that makes a small hole in the ground and damages everything around it. The hit points increase according to the selected difficulty (ranging from 2000 on casual to 5000 on brutal).
On "Night 2 Die" mode, the stank gains hit points with each appearance.
Stanks appear as boss characters on the Dead of Night mission of Co-op Missions. They are boss infested, and have high hit points. Stanks are immune to the day time cycle of the map and deal heavy damage to structures.
On hard difficulty, killing a stank with no losses for it yields an achievement.
Kill a Stank before it kills anything on Hard difficulty.
Both players receive it, no matter who killed it.