What is the ruling of Islamic law regarding a man who is married to another woman, but does not provide for her, nor give her her legitimate rights of mahr and marital intimacy, treats her poorly, and denies her his right to spend the night with her, while he treats his first wife and her family well?

It is not permissible to insult a Muslim, or to belittle them, or to oppress them. The first wife must not mistreat the second wife or incite the husband against her. The husband must treat both his wives justly and fulfill all their rights, for his wife is a trust upon him. The second wife should frequently pray for her husband's righteousness and guidance. She has the right to demand her rights and to seek a separation if the husband does not fulfill his obligations.