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