It's twofold. The first is the Mona Lisa. The second is the legal consequences coming from the disruptors turning on him. He'll be destroyed, not just his reputation but financially too.

Exactly. He feigns incredulity when she says he burned the napkin. The whole thing was the other "disruptors" protecting him with lies and then turning on him as the final beat to the plot.

One of the fun twists of the movie is that there were multiple Chekhov's guns. The Mona Lisa override switch and Bron's little saying made it abundantly clear his arrogance would result in the destruction of the priceless artwork.