True, we're very complex creatures. Negative feelings towards parents are especially difficult to process I think. If we're lucky and our care givers gave us at least some love and care- chances are we love them back. So, on the one hand, it feels disloyal to have critical thoughts about them.
We're all human though. We make mistakes, or- we don't quite match up to our responsibilities. That can be pretty catastrophic where children are concerned. I don't think it's necessarily bad to see faults in your parents or upbringing. Rather than just hate yourself for what's happened, you can see it more as a consequence of your circumstances. I guess the trick is not to hate them but forgive them for being flawed- when that's appropriate obviously. Depends on the level of abuse/ neglect/ trauma of course.
I think sometimes it used to frighten me when I questioned or felt critical towards my loved ones. Like- maybe it meant I loved them less. Maybe they would realise it and reject me for it. Or- it would REALLY upset them when I know they didn't really do stuff intentionally. In my case- they just didn't really know how to handle the situation. (With a suspected narcissist.)
Sorry though- that's kind of off-topic. Your post just interested me. Yeah- it is weird. In some ways I wonder if we do think- you've brought this on yourselves. (When avoidable bad stuff happened to us.) On the other though- I don't think many people actually WANT to hurt the ones left behind. We'd rather avoid it in fact. It's just a horrible consequence. But maybe suicide is a horrible consequence of a bad life. (Which they may well have contributed to...)