Description: Kill 3 enemies in one shotgun blast
How to obtain:
To obtain this achievement, you have to fire at enemies clustered together. It is easiest to do this at a lower difficulty, using a powerful gun against unarmored opponents.
An ideal opportunity presents itself while you are at the Soviet Installation. From the Adventure menu, select the Soviet Installation to replay it and equip shotgun. Use the appropriate card or replay the stage at the elite level. Then, walk over to the landing pad, where after the cutscene with Konstantin, you will witness a situation, in which two soldiers are stooping over a wounded one - shoot then and you may be lucky enough to kill all three of them. Otherwise, load the checkpoint and try again.
A much easier way, although there is a possibility that this will be disabled in future versions, is firing the shotgun at an explosive barrel and setting it off. If the explosion kills three opponents, you obtain the achievement.