乘人之危

Explanation: By: While; crisis: danger and disaster. To take advantage of people when a crisis threatening or harmful 　　Usage: Verb-object type; as the predicate attribute; containing derogatory, with the rebound guy 　　Source: Fan Ye Southern Song "cover the Later Han Xun Biography": "be seen to kill benign and non-loyalty are; position of vulnerability, non-jen." 　　Examples: Those ~, who made a fortune, is wicked man. 　　Results: Black cars have rust Bridge 　　Postscript: Black cars have rust Bridge 　　Riddle: Accident; ambulance Thesaurus:  go on [upon] the scamp, When a man is going down-hill, everyone will give him a push., Drum break Eight million people hammer