One very important aspect of MDZS is that characters have agency even when they lack power.
I think this is important to remember because a key element that distinguishes the heroes from the villains in what they choose to do with the limited options they have. JGY and XY's backgrounds have some similarities with WWX's own background, and JC and LWJ also have similar backgrounds. Those similarities are there to emphasize the difference in how they react to those experiences.
Before JGY is accepted into the Jin sect, he is politically powerless, but he's not without agency. A lot of JGY stans go around saying he did the things he did because he had no choice, but from the very beginning, this isn't true. The key point here is that although he is politically powerless, he still had the ability to choose what he wanted to do with his life, and he chose to pursue political power and prestige, and his father's approval. The atrocities JGY commits aren't for the sake of survival, they are for the sake of acquiring power and prestige and pleasing his father, whom he knows is human garbage.
Once JGY is a part of the Jin sect, it's true that his position isn't as good as Jin Zixuan's, but as a war hero and the sworn brother of two sect leaders of major sects, he's not in any danger of being kicked out either. What's at stake isn't his life or his livelihood, but his ascension to power and prestige. Again, he may not be the most politically powerful, but at this point, he is neither completely powerless nor without agency. This also applies to his marriage to Qin Su.
After he kills JGS and becomes chief cultivator, JGY has a lot of political power and the resources to do as he pleases. And he does. The atrocities he continues to commit, from the rape and murder of the sex workers he used to kill his father to the extermination of the Tingshan He sect down to a 9 yr old child to the murder of his own son, those things are decided on, planned and acted on by JGY. His character remains consistent from the beginning to the end. His circumstances change, but his goal remains the same, as does his willingness to do anything and cross any line to achieve it. What JGY lacked wasn't power, it was morals.
XY, much like JGY, had no power in his childhood. He was hurt by others and had no power to stop the injustice that happened to him. However, that doesn't mean he had no agency. He could still choose what to do with himself in the aftermath. And he did: as soon as he had the ability, he chose to take revenge not only on the man who wronged him, but also on a whole lot of ppl who didn't.
He is the one who comes up with the idea of turning live humans into corpses. He is the one who decided that, in order to "taint" XXC, it was okay to poison and murder random villagers who had nothing to do with any of it. XY hurts ppl because it pleases him to do so.
XY didn't become evil because of his sad childhood, he only used his sob story as a justification to blame his victims for his actions.
We also have JC, who isn't actually powerless nor a victim of injustice in any way, but insists of portraying himself as such in order to avoid having to take responsibility to his own actions. JC is a grown ass man who likes acts like a toddler. He refuses to grow up or change himself in any way, so when things don't go well for him due to his own behavior, he blames everyone but himself, effectively portraying himself as a victim of life itself. He is always saying he has no choice, when in fact he does have a choice, but that choice requires effort or growth on his part and he refuses to put in the work. What he lacks isn't power or choice, it's basic human decency.
In contrast with the villains, we have WWX and LWJ, who choose to be good even when it's inconvenient.
As a small child, WWX lost his parents and spent a few years in the streets, even then, he remains kind. When he's taken to the Jiang sect, he's faced with extreme abuse by YZY, and yes, whipping a child with an electric whip for any reason is extreme, and YZY did it to vent her self inflicted frustration. JFM, who was supposed to be WWX's guardian was kind to him, but made no effort to prevent YZY's abuse.
WWX had to hear YZY slander his mother, accuse him of being JFM's bastard or call his the son of a servant depending on her mood.
JC's behavior was also toxic: he isolated WWX, was dismissive of WWX's ideas, his excellence and also his hurts. He was comfortable using WWX however he pleased even to WWX's detriment.
Any affection WWX received at the Jiang sect came attached with a sense of debt, that was deliberately reinforced by YZY and JC, and passively reinforced by JFM and JYL. His sense of debt ultimately leads him to give JC his golden core.
During the SSC, WWX was praised for his demonic cultivation, but after the war was over, the entire cultivation world decided to make him their collective scapegoat. As WWX himself says, he may not care too much about the opinions of others, but he's still human. Being isolated and universally hated does affect him, but he still doesn't let it change him.
Despite his difficult life, when WWX sees the Jin prison camps, he still chooses to save ppl despite the criticism aimed at him for this and lack of support. WWX consistently chooses compassion even when the circumstances don't allow it. He chooses to be morally upright despite all difficulty, even if he has to do it alone.
WWX's uses his agency to decide what his priorities are, and he decides doing the right thing is his absolute priority. The one thing WWX will absolutely not give up on is his morals.
LWJ also has a moments in his past when he was powerless: he was only allowed to see his mother once a month, barely ever saw his father and was clearly not told the entire truth about his parents, whater it may be. Later on, when WWX is being made the scapegoat of the cultivation world, LWJ can't offer much help, and finds himself not knowing what he should do. Before the SSC, his home burns, his brother goes missing and his father dies. LWJ regrets having pushed WWX away, and by the time he wants to change it's too late and WWX dies.
LWJ grieved, but doesn't let the pain he experienced in the past define him. Instead, during the 13 years WWX was dead, LWJ dedicated himself to good and put in the effort to overcome his shortcomings. When WWX comes back, LWJ makes sure not to push him away again. Even when handling his jealousy, LWJ doesn't dump responsibility for his feelings on WWX, and never tries to change him. Instead, he handles it himself in ways that don't hurt WWX or others.
Anyway, this is just me ranting about some parts of fandom that insist some characters' sad childhood means they had no choice but to turn to evil, when this is clearly not true.
One of MDZS's major themes is that a sad past isn't doesn't justify being unrighteous, because even when someone lacks power, they aren't without agency. Even when someone can't choose not to experience trauma, they can choose how they are going to react to it. And taking your shit out on innocent people is always wrong, no exceptions.
