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