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