Two very different examples:
My ex was raised in an abusive home - his mother went through one abusive boyfriend after another, his consummation was the result of a rape, and his mother gave him up to foster care when he was thirteen. He turned to violence because it was all he knew, and he chose a career as a professional wrestler, because it provided an acceptable outlet for all his pent up anger and aggression.
He was diagnosed with schizophrenia and, in retrospect, it is clear that he was also suffering from PTSD. He sought out conflict in everything, and he could not stand it if someone ran from a confrontation. He often "fed" his anger, allowing himself to become enraged over little things and insisting on resolving all issues with a fight.
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Enter me - I have never liked conflict. I've always had a tendency to run from tense situations and preferred to resolve issues from a distance so I didn't have to face people while they were angry. As I entered my relationship with my ex, I had no idea about the depth of his issues, and found myself facing conflict with him again and again, getting worse and worse as his abuse of me reached a point where I became traumatized and fearful for my life.
I left this relationship, and was diagnosed with PTSD by the therapist a saw after. I have found that I am now even more wary of conflict than I was before, and tend to avoid situations that have even the slightest hint of possible tension. Before, I could stand my ground on things that I felt were worth facing a conflict, even though I didn't like it. Now, if I sense tension, I say or do whatever I can to get out of the situation quickly and avoid the conflict, filled with anxiety as I try to avoid a fight.
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Based on these two personal examples and reading through the other posts, I think a person's inclination toward violence really has nothing at all to do with whether or not they have PTSD and more to do with their natural inclination to swing towards "fight" or "flight" when their instincts kick in. Everyone will have a personal tendency to choose one over the other based on nothing more than their personality - and I think those with PTSD just have that fight or flight response triggered more than normal.
It's like that instinct was tuned in to hyperactivity - responding to even the slightest hint of danger, where someone without PTSD would only have that instinct kick in for truly life threatening situations. I think people with PTSD that typically lash out more are leaning toward the "fight" end, and those who typically dissociate more are leaning toward the "flight" end.