Here is the full list of all 43 Regain Earth: First Strike achievements.
Survive round 3
Survive round 2
Survive round 1
Kill first enemy
Survive round 4
Survive round 5
Survive round 6
Survive round 7
Survive round 8
Beat easy difficulty
Beat medium difficulty
Beat hard difficulty
Beat extreme difficulty
Win 10 Matches
Win 25 Matches
Win 100 Matches
Win 500 Matches
Win 10 Team Matches
Win 25 Team Matches
Win 100 Team Matches
Win 500 Team Matches
Kill 100 enemies
Kill 1000 enemies
Kill 10000 enemies
Kill all in one wave with headshot
Kill all in one match with headshot
Kill all in one wave with explosives
Kill 500 enemies with your Launcher
Kill 100000 enemies with your Launcher
Kill 500 enemies when they are in air
Kill 500 enemies with a possessed
Kill 10000 enemies with a possessed