I am so glad someone made this thread, enlightening to read.
My brother has been going through an abusive relationship, but he was completely blinded to it and I have been so frustrated to watch the situation grind him down to a shadow of himself.
He is on the spectrum so a bit oblivious to things and met the woman at work who became his friend (classic love bombing), and he didn't really notice she sort of inserted herself at every point of his life.
He wasn't interested in her in a romantic sense, but he had a need to be loved, cared for and appreciated and she provided that in spades. After a few months, she had more or less isolated him from every other relationship and she had made herself his mother / wife / best friend and only ally.
Then she pushed for things to turn romantic, and they did, but he was not really wanting that and was reluctant so she turned up the pressure. He describes this as the "boiling frog" analogy as so many people have mentioned.
The abusive behavior began here starting with verbal abuse, tantrums, monitoring who he was or wasn't allowed to speak to, triangulation and so on and this escalated to hitting him, harassment, threats, blackmail.
It staggered me that she was able to get away with it, but I think she did it by playing the victim very well (a lot of tears and poor me stories), and by making him feel good / special / wanted. She would more or less terrify him with her scary behavior but then come crying and ask him to look after her because she was weak / vulnerable / needy.
It played on all his weaknesses really and it took her doing something really extreme for him to end things with her because he felt quite trapped. Ending things with her has been close to impossible because she continues to use the same tactics.
He's being treated for depression and anxiety now, because I think she mentally broke him. He does see she was abusive, but for a very long time he had two versions of her in his head. One was the nice one who looked after him and needed him to be her hero, and the other one was quite terrifying.
He also, for whatever reason, has been led to believe the abuse was his fault. No matter what I do, he still thinks he "led her on" and that's why she went so man. She is very good at making him feel she is the victim. He says he feels sorry for her because she is weak and damaged and she uses this (months after things have ended) to manipulate him.
He still feels a shudder and sense of anxiety when a car drives past his house, but he doesn't seem to realise that's not a normal way to feel about your ex girlfriend who is allegedly weak and damaged.
Trauma bonds play a part, also he had familiar experiences before, low self esteem and is generally easy to manipulate. I feel like this woman ruined his life really and if she were a man she would definitely be locked up for her threatening behavior