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