I am looking for a word which can be used in emphasising that "something is very bad or good to the extent that someone else cannot believe."
For example: I may say to Joseph: "Joseph! To the extent that you cannot believe, Sarah is wicked" or "Sarah is wicked to the extent that you cannot believe".
Is there any other word or group of words I can use to explain to Joseph how wicked Sarah is without using the phrases "the extent that you cannot believe"?