Development. Pip finds his way from the graveyard and the forge at the beginning of the novel to Satis House (where he falls in love) and soon after to the city of London to live out his 'great expectations'. He develops socially by being brought into a new circle of more affluent and better educated people, such as Herbert, Jaggers and Drummle, whilst also learning a more refined set of manners and etiquette. In short his improvements are superficial and relate to material wealth and a more cultivated social behaviour.
Pip's degeneration is part of his development - the one is contained within the other. To understand Pip's moral enfeeblement and to sympathise with him (which he, looking back as the narrator of his own story, does not) the reader must realise that Pip was emotionally crippled from the start. This was due to the loss very early in his life of his close family members and by his cruel treatment at the hands of Mrs Joe. This is quickly followed by the unkindness of the vindictive character of Miss Havisham and her heartless adopted child, Estella.
All this works quickly on Pip and makes him feel unhappy with himself and the life that has been prepared for him in Joe's forge. As a result Pip becomes dissatisfied with his life, and even with those who have treated him kindly, namely Joe and Biddy. He is soon dismissive and unfeeling towards them and is only too pleased to leave them behind him when he goes to London. Pip's new found disdain is underscored during Joe's visit to London when Pip feels deeply embarrassed in front of Herbert by Joe's uncultivated manners.
It is only when Pip starts to suffer the loss of his expectations most that he begins to redeem himself. After realising that Miss Havisham has mislead him over Estella he is eventually able to take pity on her, and when he is confronted by the horrible truth that the convict Magwitch has been his benefactor all along he resolves (after initially rebutting him) to help him escape the law. One of Pip's greatest and most redeeming acts is to secure money on his friend Herbert's behalf so that the latter can set himself up in business.
I would argue that whilst the narrator finds his younger self blameworthy, the reader is inclined to be more sympathetic, regarding Pip as a tragic character who has been dealt a cruel hand by fate and who eventually learns modesty and humility only through a process of great suffering.