Re: Ok GM's weigh in. We've been talking players CvK...how do you handle these things
As a GM, I look for 'red flags' in every character's list of disadvantages/complications. "Casual killer" is a big one, as others have pointed out, but at the other end of the scale, I view any "Total" Psychological complication as the equivalent of a "Stop Sign" power, if not worse. It indicates a character who's going to cause problems. "Total" psych lims, when role-played as such, tend to result in characters who behave like they're clinically insane. They've got a hang-up so severe they're going to obsess over it, to the point of harassing and obstructing other characters, behaving completely irrationally and making things difficult.
I just try to avoid "Total" psych lims altogether, including a Total CvK of any kind, when I'm GM-ing.
What I really dread is the character who writes up a Psych lim as "Moderate" but then proceeds to role-play it as a "Total" Psych lim after it's been approved. I had someone "bait and switch" me with a "Moderate Code v. Killing" in an Iron-Age vigilante campaign once, and it was a disaster. The whole thing ended up imploding, partly due to his out-of-genre antics.