an iron hand in a velvet glove

US /æn ˈaɪərn hænd ɪn ə ˈvelvɪt ɡlʌv/
UK /æn ˈaɪərn hænd ɪn ə ˈvelvɪt ɡlʌv/
"an iron hand in a velvet glove" picture
1.

mano de hierro en guante de seda

a person who is outwardly gentle but inwardly firm and unyielding

:
The new manager has an iron hand in a velvet glove; she's polite but gets things done.
La nueva gerente tiene mano de hierro en guante de seda; es educada pero consigue que las cosas se hagan.
Despite his gentle demeanor, the CEO ruled the company with an iron hand in a velvet glove.
A pesar de su trato amable, el CEO dirigía la empresa con mano de hierro en guante de seda.