a stick to beat someone with

/ɐ stˈɪk tə bˈiːt sˈʌmwɒn wɪð/

/ɐ stˈɪk tə bˈiːt sˈʌmwʌn wɪð/

un bâton pour battre quelqu'un

something that can be used as a basis for criticism or punishment of someone