DS was very violent as a child. Mainstream school almost tipped him into being an irretrievably violent young man. Luckily he was excluded (though it didn't feel lucky at the time) and just as he was starting to be allowed back, Covid started which was terrible or his education but fantastic for allowing DS to destress at home instead of having to go daily to an environment that was incredicly toxic for him
DS stopped being violent at home around age 5 (apart from slamming doors and occasionally breaking something in his teenage years when very unhappy). He has never harmed a person in our home or even any wide family member since then. Most of my family are happy to see him and have him around. He does not scare them at all. Even aged 21 and still at home now, when he gets upset and starts to be frustrated, he will calm down if either I or DH are there and can talk to him, even if it is one of us that has upset him. I find him frustrating often but have never ever been scared he will hurt me
However, he only stopped being violent in social settings and at primary school at around 10 years old. He started being violent again at secondary school in year 9 and he stopped being violent only after he stopped going and went to a local college instead. His behaviour can still be difficult to manage sometimes and he gets incredibly anxious but he hasn't hurt anyone in 5 years, since he started college at 16 years old. I doubt he will be able to work though as I think a normal job with average stess levels will be very bad for him and if he were not allowed to be left to calm down when upset, I suppose he might possibly lash out. If he gets very upset but is left alone however, he regulates quickly nowadays.
So it is not inevitable that an excessively violent child (and DS really was excessively violent when he was younger) will turn into a violent adult but it is reasonably likely I'd say and depends on so many factors it is hard to know who will stop doing this as an adult and who won't
As someone earlier said however, it defintely requires consistent and skilled teaching and emotion coaching. DS was lucky in that 1) He had no siblings to take away from mine and DH's commitment to this which was frankly incredibly time consuming and exhausting work and would have been impossible with other children in the home 2) He was intellectually able which helped to mitigate some of the frustration and helped him understand when we were teaching him problem solving skills, 3) He grew up in a reasonably calm environment with 'goo d enough' parents. Put a child like this in a chaotic home and they have no chance at all. 4) His father is autistic but incredibly calm, non emotional, very supportive on a practical level and very successful professionally, so a good role model for DS
DS was unlucky in that 1) He has a volatile mother prone to depression, so he might have had an even better outcome if I had been able to stay calmer through out all his challenges. I did my best, read up on how best to deal with him, did training and got therapy etc but it was always a work in progress, in a way that it never was for DH. 2) He attend mainstream school. To this day I think he would have done better in a specialist placement but we just could not get him into one, we really tried.