Here is the full list of all 25 Let Them Come achievements.
100 Challenges Completed
50 Challenges Completed
20 Challenges Completed
5 Challenges Completed
Game plus mode completed
You killed 100 enemies in a frenzy!
10 000 Enemies Killed!
You completed a wave using only genades
You have come to the end but new challenges await!
You finished campaign on highest difficulty
Moving on
5000 Enemies Killed!
4 active bonuses at the same time
You discovered all the alien species
You completed a wave using only secondary items
2 active bonuses at the same time
1000 Enemies Killed!
You killed 10 enemies at once!
Perfect combo bonus!
100 Enemies Killed!
You completed the game tutorial
Thank you for your support!