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