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