ASSASSIN'S CREED ORIGINS ARCHER OF THE MONTH ACHIEVEMENT/TROPHY

For this achievement you need the "Elite Ranger" skill in the hunter skilltree. Travel back to Siwa or any other location. I prefer Siwa because here are the weakest enemies. Equip a hunter bow and aim with that bow to an nearby enemy then jump down from a higher position and during you fall in slow motion shoot the enemy in the head.