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