this is REALLY important to me as someone who has both NPD and BPD. i very often see people using narcissistic or delusional as insults and it drives me ABSOLUTELY FUCKING NUTS.
narcissistic does not mean Evil Bad Abusive Person. delusional does not mean Crazy Stupid Person With Bad Opinions. dealing with things such as narcissism or psychosis can and will absolutely ruin your life. and i mean, DECIMATE it. that's not to say other people won't be affected either, but the sufferer is the one who has it the worst. do not use words unless you actually know the meaning behind them, and who is impacted.
i should note that there are various different types of delusions, and the way to handle them depends on which specific type they are. persecutory delusions, characterized by believing someone is out to get the person in some way, may require you to be even gentler than normal in your approach due to that extreme paranoia (very common in BPD). but something such as somatic delusions characterized by thinking something is physically wrong with oneself can require a different approach.
generally speaking, the way to handle delusions is to validate the feelings caused by the delusion, without feeding into the delusion itself. this can show up as you saying "it sounds like this is really upsetting you, can you tell me about it?" this helps the person feel seen without having their delusions worsen. obviously this is not an end-all-be-all statement, but you should keep this general sentiment in mind when interacting with someone experiencing a delusion.
dealing with things such as narcissism, psychosis, psychopathy, and more is actual hell on earth which i would never wish upon my worst enemy. please be mindful of the language you use to describe people/characters because there ARE real people out there who are affected by these things. i am one of those people, as are many others.
if someone out there actually takes the time to read this, i hope you learned something! i work as a therapist and am getting my master's in clinical social work, so feel free to ask me any questions you may have about this stuff! remember to be kind <3