Here is the full list of all 18 Gravity Badgers achievements. It takes around 10-12 hours to unlock all of the achievements on Windows.
Defeat the first boss.
Defeat the first boss with a perfect score.
Lose to any boss.
Get 75 Energy Cores.
Finish all 9 Tutorial levels.
Collect 3 Energy Cores in any level.
Get 150 Energy Cores.
Get all Energy Cores.
Defeat the second boss.
Defeat the third boss.
Defeat the fourth boss.
Finish the game.
Defeat the second boss with a perfect score.
Defeat the third boss with a perfect score.
Defeat the fourth boss with a perfect score.
Play the game for a total of one hour.
Play the game for a total of five hours.
Play the game for a total of ten hours.