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