I had a problem like this in my last effort, and it cost me more sweat than anything else in that story. It was all the harder because it was a husband beating up his wife. I really didn’t want to go there and tried everything to skate round it, but the plot demanded that I meet it head-on. In the end I did almost exactly what Jonathan suggests: I went right into the victim’s head, PD5, abandoned grammar, etc. If you think it would be helpful I’ll post the passage when I get back from holiday after the weekend, and you can see if it gives you any ideas.