So can you identify no situation in which killing someone is appropriate?

If you're asking if I think the death penalty is appropriate for a system of criminal justice, then no. I do not think there is ever a situation where that is appropriate. It is immoral.

There are other situations where I think using deadly force is justified. Defending a country under military attack is one of these situations.

The reason I posted that is that I don't think belief in the greater good is enough. Believing in the greater good brought us the holocaust, for example. It is simply not enough of a reason to kill people.

> Believing in the greater good brought us the holocaust, for example.

Please do more historical research. The Holocaust was not caused by seeking the greater good, but instead the greater evil. It was caused when massive numbers of people decided that rule by terror was not worth resisting as long as it did not touch them.