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