1.  Even though he committed suicide I think Neil transformed the most through his experiences in the film. Reason being is because in the beginning he wasn't doing what he wanted and never got to actually be himself. Throughout the film he started doing what he wanted and being himself, expressing himself.
2. Cameron was the one who didn't change throughout the film. He never wanted to do what he wanted he followed the rules and just cared about his career or education.
3. Mr. Keating was an inspirational character, he made his students express themselves in ways they didn't know they could.
4. Todd Anderson fear was that he was scared he wasn't going to be as good of his student as his brother was. Neil Perry fear was he was scared to do what he wanted to do because his father didn't let him.