In fact with the utmost assiduity he undermined the rock of her purity with such engines that had Camilla been of brass she must have fallen.
I am not the one to undermine the propriety of Senor Don Quixote, for it strikes me that among his many virtues the one that is pre-eminent is that of modesty.
There are no more uses of "undermine" in the book.
Show samples from other sources
Her father had a way of undermining his sister’s lectures on the innate superiority of any given Finch: he always told his daughter the rest of it, quietly and solemnly, but Jean Louise sometimes thought she detected an unmistakably profane glint in Atticus Finch’s eyes, or was it merely the light hitting his glasses?
Harper Lee -- Go Set a Watchman
He cocked his head, trying on his "I’m so wholesome" routine, but his bloodshot eyes undermined his efforts.