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