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