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