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