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