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