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