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