居心叵测

Explanation: Motive: deliberately; thereupon: not; test: speculative. Refers to the deliberately vicious, not speculation. 　　Usage: The main predicate; as predicate, object, attribute, adverbial; containing derogatory 　　Source: Qing Lin, "the Guangdong Zougao": "and its ulterior motive, repeated often extravagant." 　　Examples: ~ He is a guy, to Duojia Ti defense. Thesaurus:  Wolf son Beast, harbour evil design, dishonorable