Here is the full list of all 21 HELLFRONT: HONEYMOON achievements.
Destroy 4 buildings and build 1 building in 10 seconds with your team
Destroy 5 buildings in 5 seconds with your player
Kill 4 players with your player without dying
Kill 2 players with your player in 5 seconds
Kill 3 players with your player in 10 seconds
Build 5 buildings in 3 seconds
80 aliens killed by anyone in 8 seconds
6 buildings destroyed by anyone in 5 seconds
12 buildings destroyed by anyone in 10 seconds
55 marines killed by anyone in 3 seconds
55 marines and 1 building destroyed by anyone in 6 seconds
4 marines are smashed by a falling building
A player is smashed by a falling building
40 aliens spawned in 3 seconds
Complete the tutorial
Complete all Honeymoon missions
Complete all Geminus missions
Complete all missions with 1 star
Complete all missions with 2 stars
Complete all missions with 3 stars
Complete all missions