How to treat a person who always likes to complain in front of the leader? What is his purpose? Is it to please the leader and increase his authority?

If someone complains, you should pretend that you don't know others' complaints and be nice to him, because if he is dissatisfied with you, there will always be people who don't like you. He won't complain when he grows up and understands. No one is perfect, forgive others. Be good at taking others. You did better. Life will be beautiful. Maybe he sued you. You will have another good way out. Really. Leaders are not fools. Everything else is measured.