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