"While using the Slug Cruiser, kill 3 enemy crew members with one shot from the Anti-Bio Beam."
To earn the Disintegration Ray achievement, a bug in the game can be exploited where a player teleporting their own crew members on to the enemy ship during a battle can then kill those crew members with a shot from the Anti-Bio Beam and they will be included in the total killed (along with any enemy crew).
Killing System Repair Drones or Anti-Personnel Drones also counts to the limit of enemy crew members killed.
Other Slug Cruiser Achievements: