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