1.Describe ideal "good death" (your opinion)(Whatever like: Organ
donor,living will,durable power of health-attorney,type of funeral
ceremony,or guardianship of children, etc....)
2.what is your opinion about "Euthansia" and who can allow someone who
is to die to go?
3.How can a nurse comfort a dying patient's family?

Your post leaves me wondering what the question is.  It's not specific
enough.  I will comment on #3.  A nurse could give a little comfort to
a dying patient's family by the following:
1.  Don't say a lot, but let them know you care a lot.
2.  If you believe it yourself, you can remind them that death is not
the end, there is life after death, and the pain and suffering will
end for the terminal patient, and death will be a great relief.
3.  Complement them on their kindness and care of their dying family member.
4.  We all take our turn, no one gets out of this life any other way.

On Euthanasia,  The dying person makes the call.  If unable, hopefully
a living will exists, but if there is not one, the nearest kin will
have to make the decision.  They should try to make the same decision
they believe the dying person would make.  Killing a person who is
terminally ill but is not on life support is not an option to most
Christians, but turning off the life support systems for a terminally
ill person is acceptable to Christians.

I realize there are no wondrful answers at a time like this.  We do
the best we can.  Good luck.