I think the difference between a Karen and someone who simply wants adequate customer service is that the Karen will tend to abuse people who a) lack the power to help as they're too far down the corporate ladder and b) will lose their livelihoods if they shout back, making it an unsporting thing to do. You're a Karen if you shriek and stamp your feet at a teenage fast food employee over chips that are too salty, you're not a Karen if you calmly but firmly escalate things to people who do have the power to solve your problem. It's the power dynamic that makes one a Karen, "punching down" is a Karenish move while "punching up" is often fair enough in my opinion.