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