Here is the full list of all 29 Second Extinction achievements.
First Deployment.
Complete the mission "Homebound".
Complete the mission "Vestige".
Complete the mission "Contact".
Complete the mission "Charged Extraction".
Complete the mission ”Research And Rescue".
Complete the mission ”Black Site".
Complete all core missions.
Complete 10 Contracts.
Complete 20 Contracts.
Complete 40 Contracts.
Respawn 20 times.
Respawn 40 times.
Respawn 100 times.
Deploy 10 times.
Deploy 20 times.
Deploy 50 times.
Deploy 100 times.
Kill 750 Enemies.
Kill 2000 Enemies.
Kill 6666 Enemies.
Play 20 missions at night.
Kill 20 Enemies with Supply Drops.
Kill a T-Rex with a Supply Drop.
Complete a mission without using a Health Stim.
Find the golden egg.
Complete a mission without any on the team having to respawn.
Unlock all perks for one weapon.
Take a raptor with you when you extract.