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