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