When an honest policeman's family is kidnapped by a sadistic crime lord, he must murder the chief of police, his father in law, to save his family from being killed

I’d leave out honest, since I’d assume as much unless I was told otherwise. I’d also leave out ‘from being killed’ since that is often implied in a hostage situation. And I’d leave out sadistic and change it with the type of crime Lord he is – such as Russian money-launderer, Mexican Drug Kingpin, etc.
Finally, I personally think it needs to be more clear why he needs to kill the Police Chief (who is also his father in law?). It seems to me that the police chief is involved in the kidnapping but really, would the guy threaten his own daughter?