Please see this.
According to the website, "Euthanasia is the termination of a very sick person's life in order to relieve them of their suffering."
As for your question, in
"end with euthanasia [for disabled, elderly, and depressed people]"
the words in the brackets modify the noun 'euthanasia', describing what sort of 'euthanasia' it might be.
However, I don't think 'end with' really works here, because the passage goes on to say "Eventually, ..."
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