Here is the full list of all 39 Nex Machina achievements.
Complete 50 feats
Reach a human combo of 50
Beat Machine City on Experienced difficulty in under 5:45
Deal a killing blow to a boss with a Sword attack
Finish a level without firing your primary or your secondary weapon
Earn 6 silver medals in the Arena
Complete a single world on Experienced difficulty without saving any humans
Complete Space Station in arcade mode on any difficulty
Save all Secret Humans in a single world on Experienced difficulty or higher
Succeed in 10 end-level minigames in a row on any difficulty
Earn 3 bronze medals in the Arena
Destroy every Secret Beacon in a single world
Reach a multiplier of 50
Finish 5 levels in a row without movement, dashing allowed
Kill every Disruptor in a single world
Dash through 3 beams with single dash
Complete Future Labs in arcade mode on any difficulty
Complete Arcade mode on Rookie difficulty
Complete Machine City in arcade mode on any difficulty
Complete Fire Caverns in arcade mode on any difficulty
Complete Crystal Mountain in arcade mode on any difficulty
Fully power up the Hero
Complete Techno Forest in arcade mode on any difficulty
Save a human while it's being harvested
Reach a human combo of 5
Discover a secret level
Kill a Disruptor
Complete a feat
Complete all achievements
Complete Arcade mode on Experienced difficulty
Complete Arcade mode on Veteran difficulty
Complete Techno Forest on Master difficulty
Complete Arcade mode on Experienced difficulty without continuing
Defeat the Beamtron on Experienced difficulty with one or more enemies still alive
Save all Humans and Secret Humans in a single world on Veteran difficulty
Clear a single world while succeeding in every end-level minigame on any difficulty
Complete 100 feats
Clear a single world on Experienced difficulty or higher without getting hit
Earn 9 gold medals in the Arena