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