un lobo con piel de cordero angolul

wolf in sheep's clothing▼(someone or something harmful or threatening but disguised as something peaceful or pleasant)
noun
[UK: wʊlf ɪn ˈʃiːps ˈkləʊ.ðɪŋ] [US: ˈwʊlf ɪn ˈʃiːps ˈkloʊ.ðɪŋ]