Here is the full list of all 21 Broken Blades achievements.
Kill 10 monsters
Play for the first time
Defeat King of Bats
Win battle with the Pigcerer, the traveling Sorcerer
Defeat Pighter, the traveling fighter
Unlock every sword piece
Defeat King of Rats
Build sword with 5 pieces
Die 10 times
Die 50 times
Die 100 times
Die 250 times
Die 500 times
Kill 100 monsters
Kill 250 monsters
Kill 500 monsters
Kill 1000 monsters
Build sword using 2 same pieces
Build sword using 3 same pieces
Build sword using 4 same pieces
Build sword using 5 same pieces