What is the ruling on exploiting people, embarrassing them, and usurping their rights despite having financial capability, and how can one deal with a person who constantly exploits and interferes in others' private lives, and speaks ill of them, while wishing to advise him and refute his slanders?

It is recommended to be sincere in your intention when striving to guide your uncle, to supplicate for him, to engage him in dialogue, and to encourage him to repent. Other means include lending him religious books and tapes. You may seek assistance from relatives or scholars who have influence over him. Furthermore, you can benefit from fatwas related to smoking, contentment, chastity, dealing with oppressors, how to invite influential people to Islam, and warning against backbiting.