So far Szeth has done some pretty not cool things. But with Nale really not focusing on the major events happening with the VP characters, it seems likely that Nale will have Szeth go and right wrongs in different parts of the land. Maybe Nale will purposely keep Szeth from crossing paths with the KR. But I think righting these wrongs, doing justice, will lead Szeth on a path of redemption, mentally.
Now we've already Nale's form of righting wrongs, he tends to go a bit extreme no matter the circumstance. I think this will be good for Szeth, I think he'll finally realize where being controlled gets him. He'll come across or a situation or two, maybe another small time character, that will change his perspective. The character/situation will show him he can do good, that he can help people.
Obviously it's going to take a while to get to that point, due to how messed up in the head and traumatized Szeth is right now, but I think it'll happen. I think it'll lead to a point where a major Character, maybe Kaladin, will be in mortal danger and Szeth will come outta no where and save the day. Again, obviously it will take more than that and more time for Kaladin to trust him, but I think it's going to lead to a very funny, dynamic relationship.