Here is the full list of all 43 DARK SOULS III achievements. It takes around 80-100 hours to unlock all of the achievements on Windows.
Discover Blade of the Darkmoon covenant.
Reinforce the Estus Flask to the highest level.
Reach the Untended Graves.
Defeat Oceiros, the Consumed King.
Reinforce any weapon to the highest level.
Defeat Ancient Wyvern.
Reach Archdragon Peak.
Defeat Champion Gundyr.
Defeat Lothric, Younger Prince, Lord of Cinder.
Reach "To Link the First Flame" ending.
Defeat Dragonslayer Armour.
Discover Rosaria's Fingers covenant.
Defeat Old Demon King.
Defeat Yhorm the Giant, Lord of Cinder.
Defeat Aldrich, Devourer of Gods, Lord of Cinder.
Defeat Dancer of the Boreal Valley.
Defeat Pontiff Sulyvahn.
Defeat the Deacons of the Deep.
Defeat Crystal Sage.
Defeat High Lord Wolnir.
Defeat the Abyss Watchers, Lords of Cinder.
Defeat the Curse-rotted Greatwood.
Discover Way of Blue covenant.
Discover Watchdogs of Farron covenant.
Discover Blue Sentinels covenant.
Discover Warrior of Sunlight covenant.
Defeat Vordt of the Boreal Valley.
Become a Host of Embers for the first time.
Defeat Iudex Gundyr.
Light a bonfire flame for the first time.
Complete all achievements.
Reach "The End of Fire" ending.
Reach "The Usurpation of Fire" ending.
Perform all forms of infusion.
Acquire all sorceries.
Acquire all pyromancies.
Acquire all miracles.
Acquire all rings.
Learn all gestures.
Reinforce a bonfire to the highest level.
Discover Mound-makers covenant.
Discover Aldrich Faithful covenant.
Defeat Nameless King.