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