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