I was a prosecutor for a while, saw the whole domestic cycle of violence all the time. Most memorable one I prosectuted was the guy whose wife was cheating on him with one of her co-workers. He went to her place of employment, confronted them in the parking lot, and put a .38 in her head. She was taken to the ER, had the bullet (and some brains) removed, and recovered.
She went back to him.
It never ceases to amaze.