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