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