• I volunteered at a suicide hotline and got a call from a woman in crisis. She had progressive brain cancer and had had many surgeries to reduce tumor growth. Between the seizures and anti seizure meds she was too debilitated to drive or care for her children and her death was basically inevitable. I didn't try to discourage her. She was a patient at the clinic that sponsored the hotline and her condition was unusual so I figured out who she was but never told her she'd talked to me.
  I've taken nursing ethics and these questions were homework. Psychopath is an easy yes, provide care according the nursing code. We routinely honor "do not resuscitate" orders so I think most nurses wouldn't interfere with a suicide if the client was fully informed and chose not to prolong their suffering.*

Oh, that's always been a tough one for me. Working in the field of mental health, sometimes it is okay to allow a person to exercise their autonomy in choosing to die, even though I am supposed to convince them life is worth living. As for chronic pain and end of life issues, that is totally their choice.

Define doing the right thing

I do the best I can, in the moment.
Speaking as a person who has been suicidal: unless I want to be stopped/saved, that’s my choice and responsibility.

Right and wrong are relative to the circumstances.
Morality isn't set in stone by any stretch of imagination.
. Also important to realize morality is a consensus of right vs. wrong thought or action.
Consensus doesn't mean everyone agrees - only that a majority do.

Who says that saving that particular life from suicide is the right thing?

Yes I am ...the person that would run into a burning building to save a life of anyone. tomorrow is another day. probably do the same for a pet....no shit.

The idea is n o b l e to save somebody's life but if that somebody isn't Noble that can ruin other people's lives what you're doing and directly by Saving a psychopath's life you're destroying other people's lives I had to think on that one it's kind of like me my ideas or my intentions are good but they came back on me in a very bad way so I guess I'm sounding like a broken record I've got to do for me first

This is a great question. I think the answer really boils down to each individual's definition of "the right thing". For instance, some folks believe preventing someone else's suicide is the wrong thing, not the right thing.

Situational ethics.
Nothing is ever all black, or all white.
You do the best you can, with what you've got, at the time.

It is always right to be compassionate. One must weigh the pros,cons and consequences if they act outside of the law if they don't have a good alibi.