My father suffered from depression. I can forgive him for that, but my god he was hard to live with. Before I understood he had depression and that was the problem between us, I just thought he was a jerk. Eventually, I broke relations with him completely. I'm sorry that this happened and that I never had a good relationship with him, but somewhere in my 40s, I just cut him out of my life. This was not out of revenge or payback. It was just a necessary step toward saving my own emotional health. It's too bad I felt I had to do that, but I decided it was necessary. Maybe there would have been a better way. But I don't know what that would have been.
I don't think situation applies to everyone suffering from depression. Some depressed people I've met are alert to their effect on others, and take precautions not to make their problem someone else's. I'm guessing it may be a struggle for them sometimes.