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.
Acquire all rings.
Reach "The Usurpation of Fire" ending.
Acquire all miracles.
Learn all gestures.
Acquire all pyromancies.
Reach "The End of Fire" ending.
Discover Blade of the Darkmoon covenant.
Acquire all sorceries.
Reinforce a bonfire to the highest level.
Discover Mound-makers covenant.
Reinforce the Estus Flask to the highest level.
Perform all forms of infusion.
Discover Aldrich Faithful covenant.
Discover Rosaria's Fingers covenant.
Defeat Nameless King.
Defeat Ancient Wyvern.
Reach Archdragon Peak.
Reach "To Link the First Flame" ending.
Reinforce any weapon to the highest level.
Defeat Lothric, Younger Prince, Lord of Cinder.
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 Aldrich, Devourer of Gods, Lord of Cinder.
Defeat Pontiff Sulyvahn.
Defeat Yhorm the Giant, Lord of Cinder.
Defeat the Deacons of the Deep.
Defeat High Lord Wolnir.
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.