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