Negredo netted his second from the spot before Manu del Moral completed the rout to set up a last-four clash with either Atletico Madrid or fierce rival Real Betis.
He said the bomber was motivated to carry out the attack because his friend was killed after Pakistani security forces stormed the Red Mosque in Islamabad last year to rout Islamic extremists holed up inside.
By the 13th minute the game was already shaping up for a Munster rout as Foley broke the Viadana line on the right wing and passed outside to Anthony Horgan.