Sentence:  Resolved that , while we most decidedly disapprove the methods he adopted to accomplish his objects , yet in his willingness to die in aid of the great cause of human freedom , we still recognize the qualities of a noble nature and the exercise of a spirit which true men have always admired and which history never <WSD>fails</WSD> to honor . 
Meaning of the word marked with <WSD> tags:  fail to do something; leave something undone