Here is the full list of all 40 The Vagrant achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Achieve normal ending
Clear the game in Hard difficulty
Unlock all achievements
Failed to defeat Shroom prime
Failed to stop Soulreaper
Failed to defeat Santiago
Failed to defeat Kumasith
Defeat Soulreaper
Achieve true ending
Unlock all entries in Note
Unlock all entries in Monsterpedia
Defeat Valerie
Acquire all recipes
Unlock all abilities
Acquire all skills
Collect 1000000 mana
Collect 1000000 gold
Acquire Sword of verum
Explore all areas
Defeat Fallen Kumasith
Consumed 100 potions in total
Defeat Shroom prime
Defeat Ground shaker
Acquire a weapon or armour with 4 runestones
Stop Soulreaper
Achieve 999 combos
Achieve 500 combos
Slay the chicken
Defeat Santiago
Slay 666 monsters
Acquire a max ranked weapon or armour
Defeat Headless horseman
Defeat Kumasith
Defeat Maximillian II
Defeat HMWV
Keep drinking potions
Defeat Esgonian general
Achieve 100 combos
Fight Soulreaper
Acquire an onion from the chef in Brocley village