My dad mentally abused my mum. He's lied to my face on several occasions, about a whole range of things from petty to extremely important. I asked him not to lie to me again, and asked him to get treatment for whatever problems he was going through - he told me he was going to see a psychiatrist, gave me weekly treatment reports etc. Turns out they never happened, he might not even have gone once. That was the last straw.
He had multiple affairs. On my brother's first day of high school, he was caught seeing another woman, the same woman he missed my sixteenth birthday to be with. On the day I received my MSc, he asked not to attend in order to see a different other woman(under the guise of a work event), and only did show up - late - when my mum essentially ordered him to be there. He was caught by that woman's husband on the morning of the graduation and nearly beaten up, as I recall we found out.
The poor guy came to my mum's house the next day to tell her what was happening pretty much in tears. I once watched one of the women he messed around turn up at a family dinner and punch him in the face because he'd lied to her as much as he did to us. There's a running joke between me and my brother that we'll probably get a knock on the door one day from a half sibling located anywhere between Glasgow and Blackburn.
He manipulated a lot of my mum's friends away from her, so me and my brother are really her only support network, and have been since I was 14 and he was 9. I've had to watch her depression eat her alive for 14 years - half of my life. My dad has offered no support, no encouragement. He has made little effort to contact me since I changed my name beyond a token text about Blackburn once or twice a year, and a Christmas card which he puts through my mum's door for no other reason than to remind her that he's still nearby, living in the house that she was brought up in, less than two miles away.
And do you know the worst part is that I would certainly have some form of relationship with him, if I ever received any kind of inkling that he cared about something besides himself for a second. But I never have.
I love my mum, and I love my brother. They're my family, and they're the two people I'm closest to in the world outside of my partner and Loki. That will never change. But I was absolutely right to cut my dad out of my life for my continuing mental health and it's not your right to tell me that I don't deserve happiness for prioritising my own health over somebody else's manipulations.