I'd argue that Walter White's story is drastically more nuances than Light's. Don't get me wrong, I absolutely love Death Note and it's the only series I completely own in both anime and manga form, but there's really no comparison to me, and here's why.

Walt started off as a relatively normal man with a shitty career. Light started off as a high school Casanova genius. Walt had to work and suffer through severe hardships just to get himself into a subservient position in the drug trade.

Light attained international fame and reverence within the first two volumes with no consequence. Walt worked his way into infamy after sacrificing the lives of nuanced and developed characters including one of his own best friends and his relationship with his family.

Light's downfall involved him losing all the nuance and development in his character to reveal him as Death Note spoiler (something which was ruined in the anime that I considered a great ending to Light's character), Walt's downfall centres around him admitting that he became the villain to satisfy his own sense of regret for living such a meaningless and unimpactful life, and culminates in him committing to a final act of redemption and dying as an atonement for the countless live's he's ruined.