怜悧狡猾な人物は信用できない。
A crafty person cannot be trusted.
狡猾 alone means 'cunning' or 'sly', but 怜悧狡猾 emphasizes both cleverness (怜悧) and cunning (狡猾), making it a stronger, more literary compound.
ずる賢い is a more colloquial adjective for 'sly' or 'crafty', while 怜悧狡猾 is a formal, four-character compound used in writing or formal speech.
A yojijukugo (four-character compound) combining 怜悧 (clever, sharp-witted) and 狡猾 (cunning, sly). The exact historical origin is uncertain, but it follows the pattern of many literary compounds formed in Japanese from kanji with similar meanings.