Hunting

Hunting is an achievement/trophy in the Chronicles Pack, a DLC for Metro Last Light.

Overview
This achievement is awarded for killing 20 Nosalises in the Khan level. The description says that the player also needs to kill a Big Momma, however, the description is misleading, as that mutant is never encountered in the level and killing it is not necessary to unlock the achievement.

Although there are Nosalises when playing as Ulman, there are not enough to unlock the achievement/trophy as him. Instead, wait until you are in the dream sequence, playing as a young Khan. The best place to unlock this is just after you have defended the barricade with your two companions. Although there are Nosalises here, your companions will likely kill too many for you to make a dent in the necessary number. Instead, wait until you are in the main station with the man called Kuzmich. When he is killed, Nosalises will spawn infinitely, around one every ten seconds. Just run around the station, killing them, and it will unlock.

Trivia

 * The attack on the station is based on the Mobius trailer, which did include Big Momma. It is possible that the Nosalis Rhino was planed to be in the level but was removed from the level for some reason, and the achievement/trophy description was overlooked.