Walter thought of himself as a master of his crasft--a scientist and an artist. Is he inherently bad or a victim of circumstances? Or both? We might know for certain; one could come with an argument to support each one.
One thing is certain: the evolution of the characters from regular people to hard-core criminals, from family to foes, from self-righteous to sheer hypocrites is amazing. You would love, hate, respect, loathe characters throughout the series. Overall a great show.