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