Complex sentence: Daoud ultimately regretted that the Palestinian operation he had conceived had backfired and resulted violence and killings which was never intended (according to him), creating a public outcry against (rather than sympathy for) the Palestinian cause.
Split into simpler sentences: Daoud ultimately regretted that the Palestinian operation he had conceived had backfired and resulted in violence and killings, which was never intended (according to him). The killings created a public outcry against (rather than sympathy for) the Palestinian cause.