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