Sentence:  "The tyrannous and bloody act is done,— / "The most arch deed of piteous massacre / "That ever yet this land was guilty of. / "Dighton and Forrest, who I did suborn / "To do this piece of ruthless <WSD>butchery</WSD> 
Meaning of the word marked with <WSD> tags:  The cruel, ruthless killings of humans, as at a slaughterhouse.