Sentence:  And, here, on the sidewalk outside was a gang of white boys come to heckle, a rag-tail rabble, slack-jawed, black-jacketed, grinning <WSD>fit to kill</WSD>, and some of them, God save the mark, were waving the proud and honored flag of the Southern States in the last war fought by gentlemen. 
Meaning of the word marked with <WSD> tags:  Extremely; lavishly.