What if the morality of assisting someone's suicide?

Let's say that a person is severely physically or mentally ill or live in an inescapable unbearable life situation. They have done anything in their power to make things better for themselves, including extensive therapy.

I'm not asking about the legality of assisted suicide, though that is a different topic of discussion. If a person really have no desire to continue living and their life doesn't improve no matter what, would it be immoral to assist them in ending it or not preventing them from doing so?