I haven't spoken to my dad in a few months shy of a decade. He abused my mom, stepmom, and stepsister, and treated me like shit when I was a kid. Calling me fat, making fun of my quietness and shyness around people ("Why would you want to go on a trip to [place]? You'd just be playing your damn Game Boy the whole time") . When I was a teen, he tried to repair our relationship by taking me to a park and hanging out, and I stupidly took him up on the offer... only for him to spring it on me once we got there that it was actually a date for him and a woman. The entire time, he just tried to impress her by using me, talking about my school grades and stuff. I felt humiliated and stupid for thinking he might actually want anything to do with me.
I stopped talking to him for good after that. The last time I talked to him was when he called me on my birthday later that year (at like 2:00 AM for some reason). We didn't really say much, I just awkwardly tried to get to the end of the call. I blocked his number and haven't heard from him since, and I don't regret it. He's a shitty person and I want nothing to do with him. As far as I'm concerned, my grandfather was my dad, not that asshole.
I've debated cutting off contact with my mom recently due to her homophobia and transphobia, but we'll see.
EDIT: Oh yeah, can't forget him calling my at-the-time best friend a (cw: homophobic slur) faggot to his face when he came out as gay. I'm glad I never came out to him.