When a couple thousand mercenaries screw up a holy site so hard that a monastic community holds a grudge for 700 years against an entire ethnicity of millions, you know it’s bad.

Context: So the Byzantines hired these Catalan mercenaries to fight the Turks. Then the emperor’s son went and had their leader murdered, and the rest of them basically said “screw this” and went on a rampage through Greece. They even sacked Mount Athos, which is a big holy site for the Eastern Orthodox monks. The monks there never forgave them, and for centuries they’d curse the Catalans in their prayers. And now the Byzantines have no money and no one to stop them. That whole dog meme fits way too well.