I wholeheartedly disagree with Walter White, actually, and a lot of the other examples.
Part of what’s makes Breaking Bad so cool is that Walter White is who he is for basically the entire show. His ACTIONS change; he goes from being a shy teacher to murdering people. his fundamental character, however, is largely unchanged; what you’re seeing is the fact that he always was a deeply flawed and ugly person inside. In the spirit of a good Shakepearian drama, he is a man of considerable talents but who has a tragic flaw - prideful arrogance - that ultimately is what determines everything he does. Everything he does, that brings him up and tears him down, comes from pride.
Michael Corleone, similarly, was a cold, calculating bastard the entire time.
Most character transformations are the result of deliberately changing things or just a character changing over time - Homer Simpson started out as a fairly conventional character, not the retarded buffoon he became. Or Ash Williams, the central figure of “The Evil Dead,” who started out as a normal person but later became a wisecracking, dimwitted clown. That just served the purpose of the vehicle, it wasn’t really a change of character.
For a good character change I am reminded of the character of Rubin Carter in “Hurricane.”