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