show someone in their true colors

US /ʃoʊ ˈsʌm.wʌn ɪn ðer truː ˈkʌl.ərz/
UK /ʃoʊ ˈsʌm.wʌn ɪn ðer truː ˈkʌl.ərz/
"show someone in their true colors" picture
1.

본색을 드러내다, 진면목을 보여주다

to reveal someone's true character, especially if it is negative or unpleasant

:
The crisis really showed him in his true colors.
그 위기는 그를 정말 본색을 드러내게 했다.
His actions eventually showed him in his true colors to everyone.
그의 행동은 결국 그를 모두에게 본색을 드러내게 했다.