The Security Breach Add-on for Showgunners has 8 achievements.
Defeat your first Stalker.
Make it through the Decontamination Zone.
Win every optional battle of Security Breach.
Decontaminate a Defender to death in the Augmentation Chambers.
Use the prototype sonic weapon in the Acoustic Weaponry Lab.
Let a Defender get obliterated by lasers in the Decontamination Zone.
Force a Stalker to go into hiding.