Here is the full list of all 20 Akka Arrh achievements.
Reach the octave with 16 pods
Arrive at the octave with 1 pod
Raise the bonus multiplier to 2.0 or more
Survive and octave
Get a hole in one
Play through tutorial levels
Get a wHOLE in none
Activate Atarification Mode
Finish the game
Reach the octave with 16 pods in HARD mode
Finish the game in HARD mode
Play from level 0 to the end
Play from level 0 to the end in HARD mode
Start a level with at least 100 bullet
Start a level with at least 500 bullets
Get 100 million points or more
Get to level 24
Hold speed multiplier at 2.0 or more for 3 levels
Activate the Egg toggle
Get 1000 bullets