a wolf in sheep's clothing

US /ə wʊlf ɪn ʃiːps ˈkloʊðɪŋ/
UK /ə wʊlf ɪn ʃiːps ˈkloʊðɪŋ/
"a wolf in sheep's clothing" picture
1.

wilk w owczej skórze

a person who appears friendly or harmless but is actually dangerous or malicious

:
Be careful of him; he's a wolf in sheep's clothing.
Uważaj na niego; to wilk w owczej skórze.
The new manager seemed nice at first, but he turned out to be a wolf in sheep's clothing.
Nowy menedżer na początku wydawał się miły, ale okazał się wilkiem w owczej skórze.