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