What is the ruling on greeting with "peace" someone who hears the Adhan and Iqamah yet does not attend the congregational prayer, especially given the existence of Hadiths that describe such individuals as "Jews of the Ummah" and warn of Hellfire for those who pray at night and fast during the day but do not attend the Friday or congregational prayers?

Congregational prayer holds a great status, and abandoning it leads to missing out on much good and reward. The preponderant view is that it is an individual obligation (fard ayn) for the one who is able. As for the hadith of Ibn Abbas regarding its virtue, it is mawquf (stopped at a Companion) and has a weak chain of narration, and something similar was reported from Ibn Mas'ud. The hadith "Greet the Jews and Christians, but do not greet the Jews of my Ummah" has not been reported. The correct one is "Do not initiate the greeting with the Jews and Christians," and to say "wa alaykum" (and upon you) to anyone among them who initiates the greeting. Boycotting one who abandons congregational prayer without a valid excuse is legislated, unless it is for the purpose of giving advice and da'wah.