Let's talk about death first for a moment. I am convinced that most deaths are miserable and agonizing.
In some cases, this is obvious. Who wants to be tortured to death by other humans? This can be extremely cruel. Skinned, boiled, burned, drowned. In earlier days, to die of torture was a common fate. See here for a gallery of historic illustrations.
Has death become better. Maybe yes, for a good number of people.
But more possible shitty death fates are actually of a newer date: Agony extended by medical science.
Many traditional kinds of death at least were over in a few minutes. But now, artificial respiration can extend suffering for many years.