Mat Cauthon was an absolute delight and Sanderson butchered him, in part because Sanderson isn't great creating characters.
One notable exception was Kaladin in book 1 and much of book 2. That was a wonderfully created and developed character. Unfortunately Kaladins back and forth angst with light eyes and Dalinar became tedious, predictable and sort of dumb. I almost looked forward to when the book would switch to focus on Shallan. Just kidding, nothing Kaladin could do could be that bad — Shallan is torture. I think Kal will become a great character again.