talón de Aquiles

Achilles heel; the weak point of a person, thing, or process

“La pandemia ha agravado un problema, convertido en el talón de Aquiles del sistema de salud alemán, que hasta el momento ha logrado resistir con cierta holgura los embates de la covid-19.” — The pandemic has aggravated a problem that has turned into the Achilles heel of the German health system, which so far has managed to withstand the onslaught of Covid-19 with relative ease.