Here is the full list of all 26 Just Shapes Beats achievements.
Rescue 250 friends (Challenge mode)
Get 25000 Beat Points
Complete 100 challenges
Obtain 15 Rank S
Get 7500 Beat Points
Complete 50 challenges
Obtain Rank S without dashing
Complete a challenge with Rank A or higher on all levels
Rescue 50 friends (Challenge mode)
Dash 2500 times (Challenge mode)
Get 2000 Beat Points
Obtain 20 Rank A
Complete 25 challenges
Dash 1000 times (Challenge mode)
Complete a playlist of all bosses
Obtain 10 Rank A
Complete a playlist of 10 songs or more
Obtain 10 Rank B
Complete a level without dashing (Challenge mode)
Complete Story
Beat 'Final Boss' (Story mode)
Beat 'Close To Me' Boss (Story mode)
Beat 'Lycanthropy' Boss (Story mode)
Beat 'Barracuda' Boss (Story mode)
Beat 'New Game' Boss (Story mode)
Beat tutorial Boss (Story mode)