My wife and co-parent of three children is a psychopath. It took me a decade to puzzle that out. She is not dangerous, not sadistic, not callous in any way you'd recognize, and not impulsive.
She can be terrifying, and she is damaging to those around her. My last three years have been about fixing the damage she did to me, and our kids. I've mostly succeeded and am divorcing her now. (There are reasons I've had to wait, please don't ask.)
She is not sadistic nor callous. Rather, she sees other people as paper thin objects to mess with. Lunch, maybe. She'll violate the most intimate boundaries on a whim. She feels no guilt or remorse, and never says "please."
She has no long term friends and even her family detest her, though are loyal. People who do not know her find her gentle, beautiful, and vulnerable. Or, incredibly rude and aggressive. It depends on whether you're potentially important or not.
Her main traits are total, infinite selfishness and the talents she needs to pull that off. She sees the world as her playground. She is the queen bee, period. If you mess with her she WILL DESTROY YOU. It is scary, her rage face, until you realize it's an act.
I will sometimes confront her and argue with her at 1/2" distance, until I get bored of it. No point. She fears nothing and just continues in her ways.
Mostly you cannot see her psychopathy unless you are watching 24/7 and spy on her email and mobile phone, like I did for a while. Then it's like WOW WTF SRSLY WTF??? She has affairs with random men, gets money from them, has multiple criminal cases against her, travels to weird places, etc. She hides it all.
The kids used to be really affected. She creates this cloud of chaos in every dimension. It's hard to describe, it's just total. House is a mess, she never sticks to plans, she can't pay bills, she steals mail, she vanishes randomly, she steals stuff, she does minimal house work, etc. See it from "I am the center of the universe" point of view, it makes sense.
I've realized psychopathy, narcissism, it's the same thing. She will dress to kill, to go shopping.
So yes, hopefully in a few months I've got a judgement against her and the kids are safe and will never have to spend another day with her, against their will...