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