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