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