have (got) someone by the short and curlies
US /hæv ɡɑt ˈsʌm.wʌn baɪ ðə ʃɔrt ænd ˈkɜr.liz/
UK /hæv ɡɑt ˈsʌm.wʌn baɪ ðə ʃɔrt ænd ˈkɜr.liz/

1.
jemanden am Haken haben, jemanden in der Hand haben
(informal, sometimes offensive) to have complete control over someone, especially by having an advantage over them or by knowing something about them that they want to keep secret
:
•
The company had him by the short and curlies after he signed that contract.
Die Firma hatte ihn am Haken, nachdem er diesen Vertrag unterschrieben hatte.
•
She knew his secret, so she had him by the short and curlies.
Sie kannte sein Geheimnis, also hatte sie ihn am Haken.