The best person in Alex’s gang. If we can say a word “best” while talking about those bad guys. Okay, he is the best from the worst. He is a very dynamic character who has changed his life a lot. After the prison and program he becomes a typical middle-class citizen, and exactly he was the one who inspired Alex to join him in the march to maturity and adulthood. He really wanted to help; he wanted Alex to feel the same pleasures of life.
That is why we easily assume that Pete is the most notable and important hero because he is the person who helped Alex to transform to the end. Pete showed it in his own example – he had a stable life, beautiful wife and in future, they will have kids. What else can an average person dream about?
You know, after reading the text it is very visible that Pete has always been the most reasonable among Alex's entourage. Pete is significant because he represents the idea that criminals can reform on their own: the idyllic life he chooses to lead in Part 3 is due entirely to his own efforts. After the program, he even went to the church to come home by Willow Cross.