As Frankenstein is a frame story, the end is the beginning, and the middle is a flashback.
So, at the end (or the beginning), Victor is half-delirious and mad (crazy). Later, once he unfolds his tale, Walton learns that his guest is good-natured and sad. Then, Victor becomes inquisitive and obsessed about knowing what Walton has seen regarding the Monster.
In telling his flashback, Victor has learned a few lessons in humility taught to him by his creation, the Monster. Victor has learned to curb his unadulterated passion, his curiosity, his reckless pursuit of knowledge, and his hubris (pride)--all of which isolate him from his friends, family, and community. All these lessons he wants to tell Robert Walton to convince him from pursuing his romantic dream, the passage to the North Pole, which may cost him many lives.
Still, Victor is hell-bent on revenge. He is obsessed with killing his monster and, it seems, himself in the process. He wants to punish his creation and himself for all the lives they, together, have killed in the process.
In his letter of August 26th, Walton comments to his sister that Victor Frankenstein brings him to tears when he "relates a pathetic incident"; Walton remarks that Victor must have been a "glorious creature" and that he is "godlike in ruin!" On September 7th in another letter to his sister, Walton describes Victor:
He spoke this [his speech to the ship's crew] with a voice so modulated to the different feelings expressed in his speech, with an eye so full of lofty design and heroism, that can you wonder that these men were moved?
Victor Frankenstein, who is initially consummed in his obsession with science and his experiments, shows little concern for others. Clearly, although he loves his family and Elizabeth, he thinks first of himself. But now, at the end of Mary Shelley's novel, Walton observes that his guest regards him "with the tenderest compassion," suggesting that in the end Victor Frankenstein becomes much like his father, thus returning to what he always should have been
He endeavours to fill me with hope; and talks as if life were a possession which he valued.
Victor even likens himself to Satan:
All my speculations and hopes are as nothing; and, like the archangel who aspired to omnipotence, I am chained in an eternal hell.
The once proud, egocentric Victor Frankenstein now is humbled and altruistic.