DJ Clark Kent, who was very much involved in Jay Z's career (from producing "Brooklyn's Finest," "Coming of Age," and more), revealed in an interview with A Waste of Time With ItsTheReal that Jay Z had a Tupac diss record.
He never released it because of Tupac's death but he did perform it at the Apollo.
"Jay did a record going at Pac but right as it was about to go out, son died. We performed it though. We was at the Apollo. It was...scathing. Crowds was like, oh shit." via Complex
According to Complex, the diss record was a response to "Bomb First," the intro cut on The Don Killuminati: The 7 Day Theory, which was the last album that Tupac recorded when he was alive.
Listen to the rest of the interview below: