Most mind-blowing vocal growth?

Who, in your opinion, has had the most mind-blowing vocal growth over their career? Like, who can you listen to on their most recent stuff and just be amazed that they've improved so much?

To me, the first people that come to mind are Oli Sykes and Keith Buckley.

If I had never heard either band, and you played their first albums for me, I would never believe they would become to of the most talented singers around. Their clean vocals are just amazing, especially compared to where we heard them first.

Thoughts?