Here is the full list of all 43 Only One achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
Mute
1 Lvl completed
Music 1
Start Game
2 Lvl completed
Music 2
3 Lvl completed
Music 3
4 Lvl completed
Music 4
1/3 of the game
5 Lvl completed
Music 5
6 Lvl completed
Middle Game
Music 6
7 Lvl completed
Music 7
8 Lvl completed
Music 8
9 Lvl completed
Pause 2
Pause
Music 9
First Restart
Game Over
First Death
10 Lvl completed
Music 10
11 Lvl completed
Music 11
End Game
12 Lvl completed
Bandit 1 Dead
Bandit 2 Dead
Skeleton 1 Dead
Skeleton 2 Dead
Fall
Go Left
Jump
Go Right
Music 12
Last Step