Does shunning a person who gossips and slanders frequently during the last ten days [of Ramadan] cause one to miss Laylat al-Qadr or affect it, and has a hadith been narrated specifically regarding that?

It is not permissible for a Muslim to shun his Muslim brother for more than three days, except for a legitimate Shar'i excuse. Shunning is a cause for being deprived of the forgiveness of sins. There is no evidence to suggest that unlawful shunning affects the reward of performing Qiyam on Laylat al-Qadr, but it has been established that animosity prevents the forgiveness of sins. A Muslim must preserve his time and not sit in frivolous and idle gatherings that include forbidden acts such as backbiting and slander.