karabiner.json

{
  "title": "Left Control -> Hyper/F18",
  "rules": [
    {
      "description": "Remap Left Control to Hyper (ctrl + alt + cmd) if used in combination with other keys, otherwise map it to F18.",
      "manipulators": [
        {
          "type": "basic",
          "from": {
            "key_code": "left_control",
            "modifiers": {
              "optional": [
                "any"
              ]
            }
          },
          "to": [
            {
              "key_code": "left_command",
              "modifiers": [
                "left_control",
                "left_option"
              ]
            }
          ],
          "to_if_alone": [
            {
              "key_code": "f18"
            }
          ]
        }
      ]
    }
  ]
}