However, if the deceased was abusive, you are not obliged to conceal a crime. Abuse is wrong, and if people don't speak out, it's just accepted as the norm and goes right on doing damage.
Another good rule is "comfort in, dump out." If the abusive deceased was a member of your immediate family, then you have every right to say whatever you want to anyone. If not, then you have to consider your stance on the above points -- let him get away with it by concealing the crime, or reveal it and upset a bunch of relatives who are already upset?
Which does the least damage is not necessarily clear. Certainly people will be upset if you speak out. But if you don't, you may hurt yourself worse, and you also lose an opportunity to encourage other survivors to speak out. What if you're not the only person he abused? What if he's not the only abuser in the family? Which are likely problems.