All types of abuse are enough. Physical, verbal, emotional, etc. People define abuse differently, and struggle to identify abusive behaviors correctly sometimes, which makes it much harder to use as a definitive criteria.
I think intentions are what really matter. Estrangement is a defensive move, done as a last resort. When I cut my mom off, it was because I couldn't handle dynamic between us and also care for my mental health. Any attempts to change the dynamic were rejected. So I made the choice to save myself. I wasn't using it to get a reaction or make her change, but to take control of my own life.
In the end, I don't think anyone has the power to tell me my estrangement wasn't justified because it was up to me. If it is justified to me, it is justified.
No one (outside of special circumstances like abuse from a spouse) cuts off a loving family. That's just how I feel about it. Where there is estrangement there is a toxic dynamic.