Rabbi, do you see the right to life as a kind of extension or derivative of autonomy? Others have no right to kill me because I am the sovereign over my own "territory"—my life.

If he has no family or friends who will mourn him, and it is clear to me that the enjoyment in his life does not outweigh the suffering, then it seems good to me to kill him!

I see value in preventing suffering, not in preventing pleasure.

You're alive only because, luckily for you, the people around you don't think like you do.

There is a distinction between the value of life itself and the prohibition against taking it. For example, one shekel has no value to a billionaire, but the prohibition against stealing it is no different from the prohibition against stealing a shekel from a poor person. That is because the prohibition against theft stems from the wrongness of the act, regardless of the value of the money (and therefore even stealing less than the value of a perutah is forbidden, even though there is no obligation to return it). Likewise, the prohibition against murder is due to the wrongness of the act of taking a human life, similar to theft, regardless of the value of that life in any particular case.

By the way, the assumption that the value of a person's life depends on the degree of enjoyment they derive from it is based on a secular outlook. The Torah outlook holds that its value depends on the fulfillment of a person's role in the world (a role much of which is hidden rather than revealed).