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
End Game
12 Lvl completed
Music 12
Last Step
11 Lvl completed
Music 11
10 Lvl completed
Mute
Music 10
9 Lvl completed
Music 9
8 Lvl completed
Music 8
Skeleton 1 Dead
Skeleton 2 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
3 Lvl completed
Music 3
2 Lvl completed
Music 2
Bandit 1 Dead
Bandit 2 Dead
Pause
Pause 2
First Restart
Game Over
First Death
Go Right
1 Lvl completed
Jump
Fall
Music 1
Start Game