2410 – I was shocked to read in your letter that in the past you have spoken disparagingly about my father-in-law the prince of Israel.

If you are completely and totally sorry you must take upon yourself and minimally also influence 10 other to study his teachings and follow his directives. That would atone for this shocking matter. https://www.torahrecordings.com/rebbe/igroskodesh/008/005/2410