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