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