Complex sentence: Abu Nidal's group was, after all, a bitter rival to Arafat's PLO and even murdered some of its members, and the PLO condemned the attempted assassination of the Israeli ambassador.
Split into simpler sentences: Abu Nidal's group was, after all, a bitter rival to Arafat's PLO and even murdered some of its members. The PLO also issued a condemnation of the attempted assassination of the Israeli ambassador.