Here is the full list of all 42 The Last Hero achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
End Game
12 Lvl completed
Last Step
Music 12
11 Lvl completed
Game Over
First Death
Music 11
10 Lvl completed
Music 10
9 Lvl completed
Music 9
8 Lvl completed
Music 8
Bandit 3 Dead
7 Lvl completed
Music 7
6 Lvl completed
Music 6
Middle Game
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
Mute
1 Lvl completed
Bandit 1 Dead
Bandit 2 Dead
Go Left
Jump
Go Right
First Restart
Pause
Pause 2
Music 1
Fall
Start Game