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