Was there ever a time when you had intended to kill off a character, but changed your mind because you liked them too much?
Hmm... I'm trying to think of whether or not this happened. I do believe that Adolin died in the original draft of The Way of Kings, which I wrote in 2002. he had a much smaller role in that book, and it played out very differently. When I did the newer version, which I rewrote from scratch, Adolin evolved much differently.
For those who don't know, he wasn't intended to have as large a role in the plot--but I ran into a problem during writing. Dalinar was feeling inconsistent as a character. I wanted to present him as strong and confident, but at the same time had him troubled by worries that he was insane from visions he was seeing.
This worked in outline form, but when I actually wrote, it seemed like he spent WAY too much time standing around worrying that he was crazy. So I expanded Adolin's character, providing a contrast. Dalinar, confident (to an extent) he was seeing something real--and his son, who worried his father was going insane.
Through this development, and giving Adolin more time on the page, he became a much more rounded character.
Another instance of this was Spook from the Mistborn series, who grew to have a much larger role than I'd originally intended.
There's another in this category--but it could include spoilers for an upcoming book. I'll talk about it eventually.
ETA: Szeth originally died permanently in the end of Words of Radiance. I also changed my mind to let Amaram live in the scene with the poison dart. Adolin killed off Sadeas instead.