Several things stand out about this transformation by Noaki Maeoka, but perhaps the most impressive is how unhealthy this tree looked when the process started and how radiantly healthy is it now

There's a lot more that you might find compelling about this transformation; like the play of the boa constrictor like living vein with the deadwood, and the finely worked deadwood at the apex. And even though I know from comments over the years, that some of you don't care much for the sculpted deadwood look, I find that it adds a daring touch that makes this tree distinctive and even memorable (if you see it again in a couple years, you'll probably remember it)

By the way, these are all the photos Noaki posted,... what he started with and what he ended with eighteen years later

Before. It's hard to tell how much of the discoloration of the foliage is poor health and how much is winter color, but it doesn't look too good to me. FYI, if your eye is untrained, by the time you notice unhealthy foliage on a conifer, especially if it is widespread, it may be too late to save the tree. 
This brings up the advantage of most deciduous and other broadleaf trees that show stress early with wilted leaves. If you're paying attention you can catch wilting early and water before the damage is serious (sometimes there's more to it, but often it's as simple as this)

After. A picture of radiant health 

Cropped for a closer look at the living vein and deadwood

If you'd like to see more of Noaki Maeoka's bonsai, here's your link to him on Facebook