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