Mark Waid has said that Irredeemable is about someone who became a superhero without being psychologically capable of being one. In the case of the Plutonian it is clear that he is much more reliant on others' opinions of him than he should be. This is one of the many causes that drives him to be evil and though you can see the origins in his earlier life it is clear that this is the immediate cause of his madness.
Note also how this madness is expressed. For all his superpowers and mind-games and cunning, the Plutonian's acts of vengeance in many cases typically resemble nothing as much a childish temper-tantrum or the actions of a schoolyard bully writ-large and powered by the strength and abilities of Superman. Essentially, he breaks things and hurts people. He wants people to like him, but when they don't react like he wants them to he lashes out. He wants respect, but like a schoolyard bully if he can't get it any other way he'll get it through fear. As well as his inspiration's moral centre, then, the Plutonian also lacks Superman's essential maturity.
This can apply to other Characters as well. Look at the Batman Expy The Inferno. He was killed off panel by the Plutonian while proclaiming his disbelief that his friend would turn on him. This is a move that is very unlike the Batman that we know as that is the kind of character that almost expects the people around him to betray him. That is how he is able to function and survive as a superhero, if not as a human being. The Inferno, though barely touched upon, shows a good picture of what Batman has to sacrifice to be the Badass Normal that he is. He had to sacrifice trust and friendship.
This also is touched on with Quibit, an Expy of The Doctor. It is shown that he is unable to bring himself to actively try and kill the Plutonian and is still looking for a way to redeem him. This does create an interesting contrast with The Doctor and The Master, where it is clear that The Master was at one point a very good friend of the Doctor he now has turned himself into a villain that, even though it may pain the Doctor, must be stopped.
With this we can see that the true intention of this comic is taking these characters and removing the basic psychological needs that they need to survive that we as readers often take for granted. In this way the comic is almost a deconstructive celebration of these characters by showing us ways in which they were great that may have never occurred to us.
The Spider-Man Paradox
Responsibility — and its corresponding assumption or denial — is a recurring theme in both Irredeemable and Incorruptible. Even as the traditional thesis statement for super-heroing comes from Spider-Man — with great power comes great responsibility — these two stories examine, subvert, embrace and reject that statement.
The Plutonian's terrible childhood was finally refined and given shape with the Hartigans — described as the only good foster family he ever had. His foster father attempted to instill complete selflessness and a sense of complete responsibility in his son. Bill Hartigan modeled perfect generosity in all that he did, and taught his foster son 'Dan' to always consider his own needs after the needs of others. Described as kind and loving but stern, Hartigan was actually as abusive as the Plutonian's other foster parents — eating desserts in front of the boy but vocally denying him any, giving him a bounty in Christmas presents then making him wrap them all back up and donate them to a children's hospital, and so forth. This ultimately rebounds on Hartigan, when he discovers that Dan had detected a cancerous growth in his foster mother but said nothing because 'you always said we should put our concerns last.' This led to Bill Hartigan committing a murder/suicide of himself and his wife — in part broken by the crushing sense of responsibility he bore — or felt he bore — for his wife's terminal condition.
When 'Dan Hartigan' revealed his secret to 'the Plutonian's girlfriend' Alana Patel, she rejects him angrily — believing he'd been laughing at her for years. She outs his identity to the radio team they were both part of, and they proceed to attempt to report it to the world — only he destroys their satellite before it can broadcast and castigates them all. He tells them he can't save them from the terrible things his enemies will do to them now, and he turns his back on them. When Patel still rejects him, he leaves her and never returns to or speaks to her again.
Patel sees the resulting horror and genocide as her fault — she sees herself as the flashpoint for all the destruction that follows. Several of her coworkers commit suicide and another overdoses, dealing with the pain. Another fakes his death but makes it clear he blames Patel for everything that the Plutonian did. Cary/Survivor spearheads an attempt to kill the Plutonian, fueled by the tremendous guilt that Bette Noir feels after she kept her affair — and the one thing that could hurt the Plutonian — a secret until it was too late and millions had died. Qubit saves the Plutonian — ironically living up to his principles in name but not practice as he kills the alian Orian to save the Earth — and Survivor proceeds to poison Qubit's name to any Qubit tries to help — seeing Qubit as bearing the responsibility for everything the Plutonian did from that moment forward. It was only later he learned that Qubit had seen a recording from the Hornet — a Batman expy — which revealed that an alien race was coming to stop the Plutonian, and so they had to keep him alive so they could live up to their side of the bargain and then leave Earth forever. Even that weighed hard on Qubit, having learned that he bore the responsibility of creating teleportation technology and sending the Paradigm out to explore the universe, only for Hornet to sell the peaceful worlds they found to the Vespa as part of his 'contingency.'
It is most explicitly stated with Bette Noir, tormented by her own sense of responsibility, escapes prison and seeks out her father, only to be rejected by him because she was responsible for the deaths of the rest of their extended family. This directly echoes the Spider-Man ethos — Spider-Man didn't stop the robber, so the robber killed Uncle Ben.
In the end, it is Max Damage who finally grows to the point of rejecting this sense of responsibility for the Plutonian's crime's. He didn't destroy the world, and neither did Alana, or Qubit, or Bette. The Plutonian did — and the Plutonian throughout blamed others and refused to accept any culpability or responsibility for it. Even when he finally found regret, that did not — in the words of his birth parents — mean he had found absolution. He, and he alone, was responsible.
Peter Parker didn't kill Uncle Ben. He didn't even allow the robber to do so. The robber killed Uncle Ben. Patel, Noir, Qubit, Max Damage, and all the others didn't destroy Sky City or Singapore — the Plutonian did. With great power comes great responsibility, yes... but when that power is misused, the responsibility for that lies with the actor, not those around the actor second-guessing themselves.
It is, in one sense, the culmination of the sense of ownership that humanity had taken in their heroes and the Plutonian — exemplified by the man who the Plutonian and Kaidan saved from pirates only to have him angrily demand they repair the bulletholes in his boat rather than expressing any gratitude. Even as so many took unwarranted responsibility for the crimes of others, so too did so many assign the responsibility of criminal acts to the heroes who saved them. They couldn't simply be grateful. They had to assign blame, and all too often that blame was cast towards the heroes who protected them instead of the villains who victimized them.
At the end of the day, Irredeemable is about a being with all the power in the world being overwhelmed by the responsibility it forced on him throwing all sense of responsibility away and lashing out at the world. Incorruptible is about a man who had always been a villain seeing that hero fall and deciding someone had to pick those responsibilities up. Both are about blame being assigned to people all around the actual instigators, and responsibility being assumed by others... and at the end both are about that actual responsibility being rejected by the innocent. Qubit was not responsible for the Plutonian's crime's because he didn't kill the Plutonian — he was able to save the world and ultimately redeem the Plutonian. Max and Alana weren't responsible for the Plutonian's fall from grace... they were only responsible for their own actions, and making the world around them a better place. And no one was ultimately responsible for the horror and death caused by the Plutonian save the Plutonian himself.