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.
Go Left
Go Right
End Game
12 Lvl completed
Last Step
Music 12
11 Lvl completed
Music 11
10 Lvl completed
Music 10
9 Lvl completed
Music 9
8 Lvl completed
Music 8
Skeleton 2 Dead
Skeleton 1 Dead
7 Lvl completed
Music 7
6 Lvl completed
Middle Game
Music 6
5 Lvl completed
Music 5
4 Lvl completed
Music 4
1/3 of the game
Mute
3 Lvl completed
Music 3
2 Lvl completed
Pause 2
Pause
Music 2
Bandit 2 Dead
Bandit 1 Dead
First Restart
Game Over
First Death
1 Lvl completed
Jump
Fall
Start Game
Music 1