I don't feel like getting into another lengthy argument with regards to all this stuff, so I'll keep my piece rather short and to the point. (fake edit: I have failed at making it short and to the point)
When I say that Jimmy is psychologically compelled to do this or has this as his fundamental worldview, I'm not trying to make a biological determinist argument. That's silly. I'm trying to point out how deeply Jimmy's scheming is seeded within him, to the point that he genuinely sees the world through a different lens than most other people. This has been proven through the multiple seasons we've seen and is as obvious as it was that Walter White was driven by his ego more than he was driven by a desire to make money or secure his family a future. Those were just the excuses, not something Walt would admit, and they were for a time believable, but you look at his actions and you'll see they don't align with someone who believes that, so you have to go for the alternate explanation that this was a matter of ego. Same thing with Jimmy. He scams when there isn't a need to scam. When he doesn't need money. He justifies it as the natural state of the world and is absolutely mystified and borderline offended when people try to encourage a moral approach that says his scamming is wrong.
This is what Chuck recognized and why Jimmy's backslide was all but inevitable and having seen all I've seen from Jimmy, I can't disagree. The only reason Jimmy even tried was because he wanted validation and that was never going to last forever. On his own, he has no intrinsic motivation or desire to be legitimate, so a version of Jimmy staying on the straight and narrow would be a version where Jimmy feels he let his life slip through the cracks for a moral virtue that he doesn't understand or believe in. I don't know if he'd have ended up as Saul, but a legitimate lawyer was never really in the cards for him and I can't imagine that ending peacefully.
But since a lot of this has been viewed as me trying to absolve Chuck of his affect on Jimmy's life, let's talk about that.
As I said, Jimmy was only chasing Chuck's example because he believed in his brother as the outstanding moral exemplar Chuck presented himself as. That's why he tried so hard to do things 'the right way'. He was given the promise that if he worked hard enough and did the due diligence, he'd eventually make it the way Chuck had. He had expected a leg up from Chuck, which he didn't get, but still that was the promise, it'd be long and hard, but eventually, he'd make it. Now, through the first season, Jimmy managed to get a hold of a million dollars and change and he had it totally untraceable to his person. He gave it back, because it was "the right thing", with Jimmy's own airquotes there because all his instincts were pushing him to just keep it. But he didn't, he did do the right thing, and he basically got nothing out of it. He would follow Chuck's example even when he didn't understand it.
It's also worth acknowledging that in all this time, Jimmy is taking care of Chuck above and beyond. He is spending money to get him food and the things he needs. Jimmy's 'dog eat dog' worldview implies that he is only looking out for himself, and this much isn't true as he is willing to go out of his way to take care of Chuck out of his own personal expense without expecting anything specific back, just the same loyalty and care he gives him.
So then he creates the Sandpiper case and Chuck blocks him from HHM yet again, and this time Jimmy catches onto what Chuck is doing. And he asks him what the hell and Chuck finally comes out with his true opinions on Jimmy. How does he respond? He goes on a scamming bender and then quits law practice. He has to be convinced by Kim that he still has a future in this career. What kind of response is this? Well, in Jimmy's view, with Chuck's pedestal shattered, I think he sees this as him falling victim to a scam. He's went out of his way to do the work, not get paid, get humiliated, etc, all that with because he believed in Chuck's promise and it all turned out to be a sham. The reason that he didn't get in HMM wasn't be cause of all the bullshit Chuck said, it was because Chuck didn't want him.
So, at this point, he renounces Chuck, but he still on some level wants to believe that a path to being a legitimate lawyer is open to him. And he still has Kim. It might be hard to remember now, but Kim was nearly as much of a paragon of legal law practice as Chuck was in those early days. She was less judgemental about Jimmy's scheming, but clearly disapproved and Jimmy kind of took her as a replacement for Chuck in terms of trying to be a lawyer who follows the moral code he sets out. That's why he takes the job at Davis and Main, at Kim's urging, and because he wants to work with her on an equal basis. If you'll recall, this was a significant part of their conflict from season 2 through season 4.
But the damage Chuck did is now irreversible and Jimmy has no compunctions about scamming to get his way. He will not be held back because of some bullshit morality that is clearly just meant to keep him down. Besides, what Jimmy does is harmless. He creates some confusion, he tells a few white lies, but no one is actually hurt, so what the fuck is everyone's problem with him doing this stuff? Eventually, Jimmy decides Kim decides that she deserves Mesa Verde as a client, so he creates the Chuck scam. And while Chuck was disapproving of Jimmy scamming others, he's infuriated at Jimmy scamming him, so he escalates. And here is where Jimmy's internal worldview is revealed - he has NO problem scamming others and getting the leg up on them, and he sees as what he does as harmless. He forces Chuck into a humiliating situation where he makes a mistake, and for Jimmy, that's nothing, just a mistake where he'd be able to "move on with his life, like a normal person". But when Chuck retaliates, Jimmy's enraged, to the point where he makes unnecessary errors and falls into another, greater trap by Chuck. Now, I want to make a distinction here because I actually agree with Jimmy that while Chuck will take his sabotage as some great crime, it's just a minor mistake that loses him money that he doesn't need, while Chuck trying to get Jimmy disbarred is a far more damaging move, it's worth noting that Jimmy never really brings it up in those terms. It's not that Jimmy is upset Chuck reacted so disproportionately, it's that he's upset that he scammed him at all. He hates being on the receiving end of a trick than the trick itself.
Regardless, this turn pushes Jimmy in more and more vindictive and cruel schemes. Meanwhile, Kim, his totem, is beyond pushed along with him. Kim believes in the law, but she also has fun with Jimmy and loves him and is willing let things slide, especially when it comes to protecting him. Even in the latest episode, after everything, she will cover for Jimmy. Jimmy is left to foster his own client base, full of criminals, so he progressively slides deeper and deeper into shady shit. Jimmy isn't trying to become a criminal lawyer, but it's what works for him the best. As he's doing this, he still dreams of legitimacy, being kind of lawyer that can stand on equal ground with Howard, Rich Sweikart, and, yes, Chuck. On a deep level that Jimmy can't acknowledge, he wants to prove them wrong, and that he has to do this shady stuff, it's either actually okay and they're too proud to admit it, or else it's a temporary setback, and he'll make his way with legitimate clientele eventually.
Which of course does not happen. The feud with Chuck escalates and Jimmy eventually wins. And then some time passes where Jimmy wants nothing to do with Chuck, but eventually, he hits a point where, yes, he wants to reconcile with his bother, so he stops by his house to make some amends...but Chuck isn't interested. He still sees Jimmy as nothing but the enemy. He tells him he never cared that much about him. And thats the last thing he says to Jimmy before he dies. From there, there's all the fall out of Chuck's death and Jimmy trying to process it, with it ending in Jimmy remembering Chuck only in terms of painful spite. He doesn't want to talk about Chuck, he doesn't want his name brought up, he only sees Chuck's legacy as what he can profit off of.
Because caring about Chuck is a sucker's game. He did all the work of trying to be the good brother, and all it ever got him was humiliated, his career set back, being moralized to, and finding out all his efforts were in waste. The only real family he had was Kim, who supports him, encourages him, loves him. And she joins him when he has a good scam idea, because she gets him. He thinks together, they're unstoppable, and they can only go up. And he keeps thinking that right up to the point where she leaves him.
That's what I think Chuck is responsible for in Jimmy's life. Jimmy was always pre-disposed to scamming and has a fundamental con-man's worldview that sees people trusting him as a reason to abuse that trust in him. However, Chuck's and Kim's and even Howards examples showed him there was more to the world than that, and Jimmy craved being a part of that world. I personally believe Jimmy would always scheme, but he would always do os with restraint, with some understanding and concern for the consequences of his actions. At the end of season 3, he schemed into getting Irene Landry to settle, but he couldn't ignore how he destroyed Irenes circle of friends, so he reversed it, destroying his entire clientele of elderly people to fix it.
This is what Chuck is responsible for in Jimmy's life. Jimmy was always going to be scheme because, for lack of a better word, that is his lifestyle. He loves doing it, it rewards him, and he can't live his life otherwise without being miserable. But he also cared about people. He would fuck with their lives if he got something out of it....but he would also try to make amends if he felt bad enough about it. I want to make it clear this is itself is limited as a redeeming element of Jimmy's character: it relied on Jimmy actually being close and personal enough with his victims to have a connection with them, he'd have just moved on if Irene wasn't someone he had to see again, and it doesn't work if he can't make up what was lost (like howards death).
But it was where the core of his human compassion was. He felt guilt sometimes. He had a small group he considered off limits to scamming. He was occasionally willing to do reparations. He cared. Chuck's cruelty and manipulativeness taught him caring was for suckers. That's what he's responsible for, abusing Jimmy's trust and love for him to the point where it hampered his ability to feel empathy for his victims. It does not make Jimmy any less responsible for his own actions, but he did damage Jimmy. That's what he's responsible for.
