Whether you think he deserves it or not, Kylo was pretty obviously being set up for redemption every step of the way. They’ve basically confirmed this saying it was the plan all along.
How though? Not in the first one, not in TLJ. What scenes pointed in that direction?
Do you want the short answer or the long one?
I’ll keep it simple. Look at his reaction to killing Han (and his scene with Snoke in TLJ that confirms it) and his final scene in TLJ. These two me, are the most indicative, but nearly every moment with him is in someway building up to this conclusion. I’m honestly baffled how anyone could miss it.