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