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