Narcissists are people who believe themselves as a exceptionally talented or beautiful or important than they really are. They want to be applauded for every bit of action they do, they are less magnanimous (less empathetic) and more of self-importance. Extreme attention seekers regardless of where they are. They never appreciate that you praising someone else in their presence.
They don’t want to be picked for mistakes they have made, they never wanted to be criticized, they don’t accept any opinion other than the points they made. They boast themselves in an irritating way while others talking about something else.
At worst, they don’t allow you to do your own job in your own way. They constantly come up with issues if things are not going by the way or the attention is not given to them. There’s plenty of other things they do to bother you and disturb the sync of any team having them.
How to handle them would make a large book of 10,000 pages. At simplest, there’s one word you can utter to them to break them inside.
“Whatever“. Use this word before any reply you want to make when they bother you. They don’t want to be ignored like this. Say the word with a tone of “I don’t care“. The tone is supposed to tell them, I don’t give a damn about your opinion and your presence. The subtle indirect meaning in the tone also includes “I am not going to praise you for anything you do and I am not going to bend for your attention-seeking tantrums”.
Instead of using “no” or arguing with them, you just ended and also open-ended the conversation with no conclusion. You didn’t agree to boost their narcissistic ego and you didn’t disagree to pull them into a fight or argument. If you want to add your opinion, add it after saying “whatever” followed by a second’s pause.
Narcissist: I am a good leader
You: “Whatever, …. I don’t mind whoever becomes a leader” (instead of saying I don’t like you calling yourself a leader and you don’t deserve those characteristics of a leader)
Narcissist: My idea is the best one
You: “Whatever,… I would wait until others give their opinions on this matter” (instead of saying: No, your idea isn’t the best one).