John Vest argues over at Adventures in Post-Christendom that rather than Satan, Walter White is best seen as a Christ figure:
The final scene brings it all together. The camera pulls out on a dying Walter White, lying on the ground in an almost cruciform pose, bleeding from a wound to his side, one palm of his hand bloodied like the stigmata. When the camera rises past the ceiling rafters, two of them make a cross over his body.
He goes on to explain how Walt's final actions can be seen as somehow salvific:
In the end, Walter White dies as a savior who manages to bring about some degree of redemption to the web of evil he has himself created.
Christ figures function in fiction in one of two ways: they either provide commentary on Jesus himself or they reflect an understanding of hero and savior from contemporary culture. Walter White is the latter. Though we have been horrified by his actions and mesmerized by his transformation from good to bad, at some level we were still rooting for him. We were skillfully reminded of this in the final episode as we marveled at his ingenious play of Elliott and Gretchen and took pleasure in his ultimate command of his situation and fate.
Whether it is catharsis or something else, it is not uncommon for us to admire and identify with the “bad guy” of the story. When Walt makes his confession—”I did it for me. I liked it. I was good at it. And I was…really…I was alive.”—we were forced to admit that we liked it too.
I was skeptical of the articles that argued Walt was a Satan-figure. Needless to say I'm even more skeptical of the idea that he's a Christ-figure. In the end, as I've argued earlier, Walt's actions show him to be human, all-too human. And thus both the allure and the horror of watching what he does comes from recognizing that what separates us from him may simply be the matter of a few bad breaks and a few bad choices.