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