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