Walter was wrong in his _answers_ nearly all the time. He was right with the _questions_ though.
<How can I protect and provide for my family> was his driving end throughout the series.
Except... he got so caught up in the means sometimes that he forgot about the end.
In the end, he drove away the people he loved, leaving only the job to keep him going. But even then, he still wanted to provide for his family first.
There's not a clear moral arc there, I don't think. You can't point to any single decision and say that was where he went wrong.