My dh was in a similar situation before meeting me. Dh found out his ex had been messaging others, he wasn't pleased about it obvs but she attacked him and tried to put a knife to him. In self defence he had to hold her down on the kitchen floor then made a run for it.
She forced her dad to take her to a&e the next day as she thought he had broken her wrist. He hadn't. It wasnt even swollen. She didn't have a scratch on her
She next contacted social services (unfortunately they have a child together) and they said they couldn't really do much unless she went to the police which they really really urged her to do....she never did.
She never went to the police because dh was black and blue. She left him with a black eye, bruised nose scratches on his shoulder etc. He should of gone to the police which I think he now regrets....
She then proceeded to stop dh from seeing their child for 3 months meanwhile not even her own dad believed her of the 'attack' and to this day only has good things to say about dh. Her dad still has so much time for him.
We got together and she wanted him back so that says a hell of a lot in itself.
So in my case, there's the other side. When dh first told me that story - which he did early on - I was very unsure of continuing with him. It was only when I saw the proof (pictures he took and messages from her basically admitting it all which he kept just incase it went any further) did I totally believe him. Over the time I've seen with my own eyes what a piece of work she is and she has bruised his arm as recently as last year (trapped his arm in a door when he said he couldn't have their child an extra night)
I do think this story is rare though. If dh didn't have the proof I'm not sure I'd be with him in all honesty