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