Is there any natural death that is actually known by medicine to be painless?

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I do not want to commit suicide, but my father died of cancer four years ago and since I am human and mortal, I do from time to time wonder about a painless death when my time comes to an end. I use to hear that pneumonia was painless and that it earned the nickname, "The Old Man's Friend", because of that - now I hear that that is not the case and that it is painful. Is there any medical certainty as to whether a painless death or anything close to it actually exists? I would appreciate hearing from anyone who knows for sure, especially doctors and nurses. Thank you.