What is the ruling on dealing with a father who is characterized by harshness and cruelty towards guests and in-laws, and is it permissible to wish for his death while seeking forgiveness for this thought?

The rights of parents are great after the rights of Allah and His Messenger. It is obligatory to show kindness to them and not to say "uff" to them, nor to reprimand them. Rather, one must speak to them with noble words, lower the wing of humility to them, and supplicate for them with mercy.

Children must endure the harshness and severity of their parents, and treat them well, just as Allah commanded to speak kindly to people, and your parents are more deserving of that. It is forbidden to wish death upon one's parents because it is a severe form of disobedience.

Parents can be reminded of the verses and hadiths that call for good character and gentle treatment of visitors, such as the hadith: "Indeed, a man attains by good character the ranks of one who prays at night and fasts during the day." And Allah dislikes the rude, harsh, arrogant, and miserly person.