It would be nice to have words that distinguish this being applied to the innocent vs the guilty
> If you don't do X for me, I will harm you physically. There are plenty of X's that will not be illegal, but harmful to reputation.
You're describing extortion. Blackmail is typically the use of harmful information to get something one wants against the other's will. Regarding the thing being obtained being harmful to the victim's reputation, it sounds like you have it a bit backwards.
Moreover, blackmail statutes often specifically cover situations in which the person being blackmailed actually did commit the crime, the threatened disclosure/allegation of which is being used to obtain something against their will. Hence, blackmail is certainly not limited to innocent victims but instead includes blameworthy ones.
https://legalclarity.org/extortion-versus-blackmail-the-core...
Reading a few of these, it seems like extortion is specific to obtaining property. Blackmail by contrast is "money or something of value" and is rather flexible in the method applied. There are a host of other words for other specific situations too.