Killing is unnecessary
Killing everything (or even knocking them unconscious) is not necessary and may not actually be even helpful, running away/past from the opponents is often as good option if not better.
Alternate name: Defeating enemies is unnecessary
The first video game about Killing is unnecessary was released in 1983.
"Killing" should not be taken literally. Games where you defeat opponents in non-lethal manner also count towards countering this tag. This tag is to signify that significant portion of the enemies can be left completely alone (gone past of by walking, running, stealth, negotiated with, etc.) without doing it in a personal challenge kind of way (non-lethal weapon use).
This does not necessarily mean killing is completely avoidable, only that significant portion of it is. Boss battles being a common exception which can be ignored for this.
* The enemies do not actually block progress and are very easy to avoid (jump over, jog past them, etc.)
* Optional stealth makes most encounters equally optional
* The enemies can be easily distracted away from where you need to go