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