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