You will get the achievement after you defeat the boss (there will be 3 stages in the bossfight, be very careful in the 3rd stage).
The boss fight is not so hard, just be careful, and avoid the "mines".
Though, getting to the boss through the traps and platforms (before the village) was the hardest part of the game.
Tip: after all the jumps and collapsing floor, you have to double jump at the final stage (after the stairs and the collapsing floor). Time your jump correctly and you will make it (i have tried to jump over at least 20-30 times but i failed).