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