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