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