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