heel of Achilles

Now, and for the last forty years, the condition of the Roman States is the heel of Achilles of the Catholic Church, the standing reproach for adversaries throughout the world, and a stumbling-block for thousands.

From The History of Freedom by John Emerich Edward Dalberg Acton, Baron Acton

Our great author had indeed the heel of Achilles.

From Amenities of Literature Consisting of Sketches and Characters of English Literature by Isaac Disraeli

In their existing extent and position, they were simply the heel of Achilles, the vulnerable spot, through which secular foes might wound the Vicar of Christ.

From Henry VIII. by A. F. (Albert Frederick) Pollard

I bethink me, the rabbi said there was one peril against which the elixir could not guard me—one vulnerable point, by which, like the heel of Achilles, death might reach me!

From Auriol or, The Elixir of Life by W. Harrison Ainsworth

I chanced to discover that Simon's heel of Achilles was his fear of death, so my next scheme was a pious plot to frighten him into behaving like a human being and a good citizen.

From The Monk of Hambleton by Armstrong Livingston