Narcissistic cofounder experiences?

What’s been your experience with narcissistic cofounders? I’m doing some research to help founders avoid the signs and traps. I’d like to be clear and acknowledge that the term “narcissist” gets thrown around a lot. There’s a difference between the full blown personality disorder and narcissistic personality traits. That many have. Some would argue you have to be a bit of a narcissist to be successful in business. I’m talking about traits like insecurity, control, inability or refusal to experience shame. A grandiose sense of self that leads to overt or covert dysfunction and destructive behaviors. Professional love bombing or emotional injury and manipulation. I once worked for a family office run by a grade A narcissist that, after years of therapy, I believe has full in NPD. Almost cost me my marriage. I’ve also had cofounders with narcissistic traits that have been emotionally abusive and sabotaged success. I was susceptible for a long time until I got the help I needed. So, I table this topic not to vent or tear anybody down. These days I have compassion for founders that show these traits but can’t see their own self-sabotage. As an advisor I meet them every week. I’m curious as to how pervasive this problem is and what discussions would be productive. Startups are hard enough without cofounder dynamics. Thanks in advance and happy new year to you founders!