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