I meant to come back to this:
But I wonder if labelling the perpetrator as "bad" is too easy in terms of beginning to understand what drives the behaviour,whether change is possible and where societies responsibility lies in addressing why this is so widespread.
Labels like that don't help much, no. But I look at the bullies & manipulators I have known best in my life and I see that some would have wanted to change - and couldn't - while others perceive no cause for change, so wouldn't. Therefore, they are what they are. Which, actually, is what they all say at some point.
My father was sadistic and full of pain. He was, taking the sum of his words & deeds into account, a bad person. This fact pained him. He did a lot of very good things but his thought and intents were not good. His good deeds were done when there was no loss to him, by his standards. The nature of his standards meant he'd choose the 'bad' thing if both options were equal in terms of benefit to him.
My mother is not at all a 'bad' person. She is, however, defined by what the world reflects upon her. This makes her harmful, without harmful intent: the way children do harm. We were talking about meditation: she says she doesn't need a method, as when she's in a static situation she can "fold in on herself". I've often seen her do this. I asked what she found inside. "Nothing," she says, "It's completely empty; I feel peaceful." She is a multi-faceted, mirrored surface and no more.
My intuition about X1 is that he's full of yearning. His childhood wasn't good, but he believes it was good and just. He, too, desires a great deal of validation - he's a classic Narcissist, complete with beautiful possessions, popularity, mood swings, tantrums and self-obsession. I'd say the self-obsession is his defining quality. He does good things and thinks he's a good person, but doesn't actually care about others' welfare. He would only consider changes that further enhance his public image.
X2 has an autistic-like misunderstanding of people and the world around him, coupled with hyper-sensitive vision & hearing. He is a brilliant mimic. His world construct is that of a zero-sum game, which he must win, and he has no moral compunction to limit his tactics. He really enjoys putting one over on people. My intuition is that his emotions are restricted to fury, resentment and triumph. He doesn't care what people think of him and has no wish to change at all, as he often says. I feel he is empty inside, too.
Crazy ex-flatmate is a lot like X2 - they got on very well together, though neither liked the other - but with X1's vanity attached. Despite sharing 7 years of our lives, I never found out what was 'inside' her and I don't think she wanted to look. Perhaps she was both yearning and furious? She fits the NPD profile exactly. As long as she gets constant adulation, at someone else's cost, she doesn't want to change. When she loses her main supply (10 years, for her) she simply moves to another feed.
So ... I'm only interested in these people's inner selves to the extent that they teach me about my own dysfunctions. They won't change because they can't, and wouldn't choose change if they could. I can characterise them as 'bad' because they harmed me - some unintentionally, but the harm was real. They were able to harm me because I was over-invested in forming positive relationships with them. Essentially, I hoped they would change ... into rounded characters with the full range of emotional & cognitive expressions. That was, I think, unrealistic and wasteful of my efforts.
I'm interested to know why you want to see if they can change, green?