I am sure YOU are NOT (●'◡'●)ノ but I think they were more saying what happens when you have a character that is BOTH a narcissist and toxic but maybe I am wrong and I misread that but that's what I got from Black Lavender's comment.
As you said not ALL narcissist people are toxic in fact one of my yaoi mangas has an uke as a narcissist which brings a LOT of humor and cute scenes between the couple.ヾ(❀╹◡╹)ノ~
So yeah nothing wrong with being narcissist but I definitely DON'T like toxic characters in stories but don't mind so long as they get what's coming to them in the end. ╮( ̄▽ ̄)╭
https://en.m.wikipedia.org/wiki/Narcissistic_personality_disorder
https://www.instagram.com/p/B4s4idhnRf8/?igshid=pmt7w0n8ifl0
A little bit of research is always worth it!
The prince is a live example of a toxic person. Here are the signs:
1. See how the marchioness thinks he's kind, but Nora believes otherwise. Toxic people especially narcissists tend to charm people during first impressions. I mean, look at the continuous compliments flowing out of the prince's mouth naturally, right in front of everyone. It's like he put effort into them.
2. He's blaming Nora for getting distant indirectly and tried to make him look bad in front of everyone, especially his parents. MC then concludes that his personality is worse than Jeremy's. Narcissists tend to manipulate people's perception of others so subtly and easily. And they always make the ones who know their true nature look bad and crazy, always with success. Notice how Jeremy smoothly avoids him too after being called out as a childhood friend.
3. Seems like crown prince is targeting MC and has used words like, "It's alright to grieve when you are alone" to let her guard down. And he's getting way too close quickly for the ice to break. She was left crying in the end. These people like to manipulate emotions and make others cry.
Like bruh, seriously, you say it's the first time meeting her and yet you had the audacity to make her cry? Leave her alone and let her marry Nora.