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