Halo: The Master Chief Collection

The achievement can be earned in campaigns as you progress. Hunters (big guys with tower shields and BFGs) are present in many missions in different parts of the saga. There is a faster and easier way to get the achievement - create a map for a shootout in Halo: Reach. Here you can set up waves of enemies and select only hunters, and our character, in turn, can be given 300% damage, immortality, acceleration and all sorts of other goodies.
The same system works with other achievements for the number of enemies killed, except for knights, observers and creatures of the flood - they simply do not exist in Reach.