minecraft-assets/assets/minecraft/advancements/adventure/sniper_duel.json

{
    "display": {
        "icon": "minecraft:arrow",
        "title": "Sniper duel",
        "description": "Kill a skeleton with an arrow from more than 50 meters",
        "frame": "challenge"
    },
    "parent": "adventure/shoot_arrow",
    "criteria": {
        "killed_skeleton": {
            "trigger": "minecraft:player_killed_entity",
            "conditions": {
                "killing_blow": {
                    "is_projectile": true
                },
                "entity": {
                    "distance": {
                        "min": 50
                    }
                }
            }
        }
    }
}