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