In Chapter 24, how is Victor able to justify his early treatment of the monster?

Basically he explains that he has taken the time to go back tp analyze his actions, and that he feels partially responsible for them, although he was acting "under a fit of enthusiastic madness" that led him to try for an ambition that was too big even for him. He even claims that he would have done anything to assure the creature's "happiness and fulfillment" , but that since the creature ended up being so evil and killling all that Victori loved, now he wante to avenge it.

Furthermore, Victor even plays himself as a good guy by saying that, out of this same feelings, he refused to create a partner for the creature. Hence, he was almost saying that it was his god kidness what saved the world from a culture of monsters, and it was all out of scientific ambition and good plans for the creature that he embarked on his experiments. We know that such thngs were all lies.