Here is the full list of all 42 ELDEN RING achievements. It takes around 80-100 hours to unlock all of the achievements on Windows.
Achieved the "Age of the Stars" ending
Defeated Lichdragon Fortissax
Defeated Mohg, the Omen
Defeated Shardbearer Malenia
Defeated Loretta, Knight of the Haligtree
Defeated Dragonlord Placidusax
Defeated Hoarah Loux the Warrior
Defeated Maliketh the Black Blade
Defeated Godskin Duo
Used kindling to set the Erdtree aflame
Defeated Fire Giant
Defeated Astel, Naturalborn of the Void
Defeated Shardbearer Mohg
Upgraded any armament to its highest stage
Defeated Commander Niall
Defeated Valiant Gargoyle
Defeated Shardbearer Morgott
Defeated Godfrey the First Lord
Defeated Elemer of the Briar
Defeated Shardbearer Rykard
Defeated Godskin Noble
Defeated Royal Knight Loretta
Defeated Rennala, Queen of the Full Moon
Defeated the Red Wolf of Radagon
Restored the power of a Great Rune
Defeated Ancestor Spirit
Defeated Regal Ancestor Spirit
Defeated Mimic Tear
Defeated Shardbearer Radahn
Defeated the Leonine Misbegotten
Defeated Magma Wyrm Makar
Defeated Dragonkin Soldier of Nokstella
Defeated Shardbearer Godrick
Defeated Margit, the Fell Omen
Arrived at Roundtable Hold
Obtained all achievements
Achieved the "Elden Lord" ending
Achieved the "Lord of Frenzied Flame" ending
Acquired all legendary armaments
Acquired all legendary ashen remains
Acquired all legendary sorceries and incantations
Acquired all legendary talismans