Sentence:  The Begums' ministers, on the contrary, to extort from them the disclosure of the place which concealed the treasures, were, ... after being "fettered" and "imprisoned", led out on to a scaffold, and this array of terrours proving unavailing, the "meek" tempered Middleton, as a dernier resort, menaced them with a confinement in the fortress of Chunargar. Thus, my lords, was a British garrison made the <WSD>"climax</WSD>" of "cruelties"! 
Meaning of the word marked with <WSD> tags:  An instance of such an ascending series.