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