Here is the full list of all 25 Harvest: Massive Encounter achievements.
Had 20 or more active harvesters before level 11.
Has linked 100 or more Defense Towers.
Killed an alien in mid-air.
Established a base on Hephaestus and reached level 15 without losing any buildings.
Defeated a wave without losing a single building.
Reached level 50 on any planet.
Reached level 100 on any planet.
Reached level 100 on all planets.
Successfully completed the Rush game mode on any planet.
Successfully completed the Rush game mode on all planets.
Successfully completed the Wave game mode on any planet.
Successfully completed the Wave game mode on any planet in less than one hour.
Reached level 50 in the Insane game mode on all planets.
Reached level 50 in the Insane game mode on any planet.
Launched an Overcharged Energy Link and killed at least 5 aliens.
Had at least 50 active harvesters at the same time in Normal game mode.
Beat Rush game mode on any planet without losing a single building.
Accumulated 1000 or more kills with a single Defense Tower.
Expanded the map considerably, on any planet.
Expanded the map considerably, on all planets.
Had 50 or more over-heated Energy Links at the same time.
Launched all 10 waves at the same time and survived.
Killed 20 or more aliens with a single overcharged Energy Link.
Defeated a wave before 15 minutes have passed.
Has been awarded all other achievement awards!