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