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