It is really hard to break it off with these men!
I know from my own x and from listening to hundreds of MN-ers, they don't accept that a relationship has to be wanted by both parties. When you try to break it off they will literally argue you into the ground, as though the relationship continuing or not continuing was a court case. They are the prosecuting barrister (if that's the right legal jargon).
But hold firm. JUST because somebody is temporarily saying something a little bit nicer to you than they had been saying to you up 'til now, that doesn't mean you're obliged to go out with this person!!
We have been conditioned by the end of the relationship to believe we are cold hard bitches for not giving them another chance.
I advise picking a phrase that can't be argued with.
For example, if you say "that time when I was sick and you didn't help me...." it'll get you nowhere. They'll just counter that with their side.
You're better off not bothering even to try and make him see^. He'll never* see. So just pick a phrase that can't be argued with and repeat it ad infinitum.
eg, I don't want this anymore.
This is how I mentally escaped from my x. Whenever he told me what a crap girlfriend I'd been, instead of defending myself, I'd just say "I don't want to you either" or "I am disappointed and let down myself".
My x only let go of his 'argue-grip' on me when I stopped defending myself, and stopped trying to 'make him see'.