As with all Psych Lims, there are two sides to the CvK: Frequency and Intensity. Frequency represents how often the Limitation is expected to come up in play. Partly, this depends on how "lethal" the campaign world is. But since that variable is controlled by the GM, what matters most to your characters is who/what they won't kill. "Won't Kill Humans" is worth more than "Won't Kill Women," but might be worth less than "Won't Kill Any Sentient Life" depending on how often the characters find themselves fighting non-human sentient life.
Intensity represents the character's commitment to the code. So "Only kills in self-defense" is worth less than "Only kills when it's the only way to save others," which is worth less than "Never kills unless it's the only way to stop the apocalypse," or even "Never Kills, period." It is possible to have a CvK with low frequency and high Intensity, or vice-versa.
CvK does not mean never using Killing Attacks, but it does mean not using attacks that are likely to be lethal or crippling. This is a subjective call based on what your character has reason to believe. A 10d6 Energy Blast against most normals is probably excessive, but against Doctor Destroyer a 4d6K Armor Piercing Killing Attack to the faceplate might not be unreasonable. This doesn't mean you have to start every fight at half-power and escalate 1d6 at a time until you've established exactly how tough the target's armor is, but it does mean you should think before you shoot. And Batman Begins notwithstanding, CvK also implies "�and won't let people die either." Yes, that sometimes means running into the burning building to save the stupid mooks that were shooting at you a moment ago; I never said being a hero was easy!
Now it is sometimes possible to violate a CvK (or any other Psych Lim). The rules require an EGO Roll to overcome a Strong Psych Lim, or an EGO Roll at -5 to overcome a Total Psych Lim. But I'm more interested in how extreme the circumstances are and how you roleplay it than what the dice say. If violating your CvK-Total is absolutely the only way to avert the apocalypse, and you feel strongly that's what your character would do, we might decide to go that route. But it should be A Big Deal�a defining moment in the character's career, full of soul-searching and repercussions down the road.
Now the good news: prisons in my world are not quite the revolving doors they seem to be in the comics. So if you turn a supervillain over to the authorities, you can have a reasonable expectation he will be off the streets at least for a while. I'm not saying villains will NEVER break out to fight again, but I expect it'll be pretty rare.
So anyway, here are some campaign-specific guidelines:
Because this is a 4-color Bronze Age game, the campaign default is for all NPCs to have, at a minimum, "Reluctant To Kill" as a 0-point Disad. Such characters will generally only kill in self-defense or defense of others. Characters that do not have Reluctant To Kill (the Punisher, et. al.) generally have other Disads to reflect its absence, such as Psych Lim and/or Reputation "Casual Killer."
|5 pts||Uncommon||Won't kill humans, but anything else is fair game.|
|10 pts||Common||Won't kill any sentient life. Non-sentient animals or monsters are exempted.|
|15 pts||Very Common||Won't kill any life, sentient or otherwise. Robots and zombies don't count.|
|+0 pts||Moderate||Won't kill unless it's the only way to save other lives, and only when it becomes clear he/she has no other options. Won't generally stand by and let someone else die, even if that person "deserves it."|
|+5 pts||Strong||Won't kill except as an absolute last resort, and even then only to save large numbers of other lives. Will risk own life to save the lives of villains and mooks.|
|+10 pts||Total||Won't kill. Ever. The ends do not justify the means. Will go to extreme length to save the lives of even the most unredeemable villains.|
The above are general guidelines only; specifics will vary some from character to character. The default for PCs is Common, Strong (15 points). You can always go higher than that (Very Common and/or Total) if you feel it fits your character concept. Going lower than Common, Strong requires GM approval.