Full list of all 78 For The King achievements. It takes around 80-100 hours to unlock all of the achievements in the base game on Windows.
The base game contains 72 achievements, and there is 1 DLC pack containing 6 achievements.
Defeat 100 Beastmen
Reach the Inferno
Reach the bottom of Hildebrant's Cellar
Defeat 10 Mimics
Defeat the Chaos Beast
Defeat Vexor on Journeyman
Defeat Vexor on Master
Crush 25 Imps
Survive the Lava Dungeon
Clear the Flooded Crypt
Murder 30 Hags
Defeat the Old One
Honor 50 Stone Heros
Escape the Mage Dungeon
Win a game of Gold Rush
Defeat the Sea King
Find Captain Greenbeard's Ship
Purge all 4 Water Temples
Defeat the Songstress
Get killed by a suicidal enemy
Kill 30 Fishfolk
Slay the dragon at the top of Frostbite Peak
Have 5000 Gold
Unlock the armory
Kill 5 Snowmen
Defeat the Yeti, free her "prisoner"
Complete 50 Side Quests
Smash 150 Skellys
Break a sieged town
Help Hildebrant retrace his steps
Unlock 40 items from the Lore Store
Unlock 20 items from the Lore Store
Defeat Vexor on Apprentice
Reach the top of Harazuel
Kill 1000 Enemies
Kill the Kraken
Purge the Buried Temple
Fly in the Air Balloon
Clear both Demon Caves
Topple 15 Crag Monsters
Defeat the Royal Droll
Clear 5 Sea Caves in 1 game
Defeat 3 Triclops
First party wipe
Use 100 herbs
Have 1500 Gold
Honor 15 Stone Heros
Use 10 candies
Kill 10 enemies with Firearms
Unlock 1 item from the Lore Store
Solve the King's Maze
Defeat Coal Heart
Defeat the Lich's Crypt
Defeat the Foul Priestess
Defeat Deimos
Defeat Disciple
Defeat the Bandit King
Defeat the Mind Bender
Find Bradach's Cabin
Enter Hildebrant's Cellar
Have 300 Gold
Defeat the Hangman
Clear the Forgotten Cellar
Defeat Lucky
Honor 3 Stone Heros
Clear a Cave
Break a weapon
Kill a thief attempting to flee
Purge the Glittering Mines
Revive a party member
Complete 1 Side Quest
Defeat the Cultist Camp