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