Euthanasia - Dirty word?

Euthansia. Everyone has a different opinion, those for and against. And within what is considered Euthanasia, different types, (BBC quoted):-

Voluntary euthanasia

The person wants to die and says so. This includes cases of:

asking for help with dying
refusing burdensome medical treatment
asking for medical treatment to be stopped, or life support machines to be switched off
refusing to eat
simply deciding to die

Non-voluntary euthanasia

The person cannot make a decision or cannot make their wishes known. This includes cases where:
the person is in a coma
the person is too young (eg a very young baby)
the person is senile
the person is mentally retarded to a very severe extent
the person is severely brain damaged
the person is mentally disturbed in such a way that they should be protected from themselves

Involuntary euthanasia

The person wants to live but is killed anyway.This is usually murder but not always. Consider the following examples:

A soldier has their stomach blown open by a shell burst. They are in great pain and screaming in agony. They beg the army doctor to save their life. The doctor knows that they will die in ten minutes whatever happens. As he has no painkilling drugs with him he decides to spare the soldier further pain and shoots them dead.

A person is seen at a 10th floor window of a burning building. Their clothes are on fire and fire brigade has not yet arrived. The person is screaming for help. A passer by nearby realises that within seconds the person will suffer an agonising death from burns. He has a rifle with him and shoots the screaming person dead.

A man and a woman are fleeing from a horde of alien monsters notorious for torturing human beings that they capture. They fall into a pit dug to catch them. As the monsters lower their tentacles into the pit to drag the man out he begs the woman to do something to save him. She shoots him, and then kills herself.

Where do your beliefs lie? for or against?