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