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