From Halopedia, the Halo wiki

This article is about the Halo: Spartan Assault achievement. For the multiplayer medal, see Extermination.

Extermination is an achievement in Halo: Spartan Assault, exclusive only to the Xbox 360 and Xbox One versions. It was released along six other new achievements in December 2013. The achievement is awarded for killing at least 10,000 enemies in co-op mode. It is worth 30 Gamerscore on the Xbox 360 and 60 Gamerscore on the Xbox One. It is represented by a circle with an Infection symbol inside it.[1]