How to deal with a traumatic past? Confront and demand accountability from those who have trespassed against us? Or forgive and forget, letting bygones be bygones?
An existentialist Adlerian answer.
First of all, bygones are bygones, and if you won't let go of them as something that has a hold on you, the question is what for. Of what use is the trauma to him who will not take the finger out of the wound?
Mind you, I'm not saying pretend like nothing happened! There may be good reasons to shun those who have mistreated us in the past, willingly or not. But, if you can, spare yourself the drama of decrying having suffered irreparable damage! You're not a car or a bridge, but a human being, and most likely with all your limbs and organs intact. Maybe you're uniquely challenged as a result of parental abuse you suffered, I don't know. Most victims of imperfect parents aren't even that, they are just averagely challenged like most everybody else. Most of those who now cry “trauma” enjoy holding a grudge and having somebody to blame for some shortcoming or two in their life that they are too avoidant to truly tackle.
As an aside: On the other hand, there are those who need to learn to actually feel anger towards a parent in the first place. Because they are in fact still under that parent's influence, and the abuse still goes on in some form.
The important thing is that, unless you like where you are, you should get on your way and move on as soon as you can. Wallowing in outrage, and demanding satisfaction is not going to do anything for you; you're not likely to get it, so you can waste a lot of time on going after it; and if you do get it, then most likely your parent wasn't such a monster in the first place, and maybe it's you who's been having the personality disorder all along.
What does help, however, is working this through in therapy, which is also the appropriate place for bemoaning that lack of love, care and protection we may have suffered; with a little help, fear and rage can be overcome by accessing the sadness surrounding those sorrowful events and times; feeling the sadness, and mourning what was unfulfilled or lost: that's what permits laying down the grudge being held, letting go of what has a hold on us.
Really, what is now commonly called trauma mostly is a case of being stuck in one of the first four of the five stages of grief, typically anger or depression. In a childhood trauma, what is grieved is the undue loss of innocence. What you want to do, is to transcend that stage through healthy grieving, and settle in acceptance. Whether or not this eventually leads to forgiveness depends on other life choices and aspirations, and I wouldn't push to make it an objective. But you know what they say: that you have to forgive to forget. And forgetting something is a sign that this something has truly healed in.
Anyway, at this point in the therapy, the loose thread of the first half of this write-up can be picked up: the question of what the person has been holding on to his hurt so dearly for, in the first place. Wherefore the scapegoat?