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