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