It is incredibly hard when people who knowingly do wrong get to walk away whistling happily and others are left to pick up the wreckage they leave behind. I feel your pain.

Things that we can do about it, off the top of my head:

* Make sure we are aware of people's red flag behaviors in future.
* Warn others about abusive behaviors. Some people volunteer to talk to the public about various kinds of abuse, for example.
* Something that helps me - for every painful thing I experience or see others experience, I go out of my way to make a difference in someone's day and try to take better care of myself.
* Talk to people in the political and legal system when it seems to be sleeping on the job. Procedures can be improved.
* Talk with a counselor and other people who have experienced similar situations. Going through anything alone can be difficult.