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