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