src/main/resources/builtin/loot/entities/vindication_illager.json

{
  "items": [
    {
      "default": {
        "count": 0,
        "item": "emerald"
      },
      "conditions": [
        {
          "condition": "ENTITY_KILLER_PLAYER",
          "count": {
            "max": 1
          }
        }
      ]
    }
  ],
  "experience": {
    "count": 5
  }
}