Send Custom Validation Error to Front

[msslgomez]

How can I return custom validation errors to the frontend from the server?

I've tried all these different ways but none work well, where $message is any ramdom string

throw ValidationException::withMessages([
'pop_objects' => $message
]);

$validator = Validator::make([], []); // Empty data and rules fields
$validator->errors()->add('pop_objects', $message);
throw new ValidationException($validator);

abort(500, $message);

return redirect('pop-helper/deliveries/create')>withErrors($validator)->withInput();

throw new Exception($message);

In my Vue file I get the event but I can't get the custom message itself which is the important part.

 Inertia.on('invalid', (event) => {
            console.log(`An invalid Inertia response was received.`)
            console.log(event.detail.response)
            event.preventDefault()
        });

How can I do this?