With King its more a lack of emotive sensation rather than actual loss of physical feeling... he can still feel pain, get the emotional reactions to that pain have gone, things like fear, dread, suffering... they have all pretty much faded away into nothing... pushed out of his mind by his 'awakened' state...
Previously, the logical chain reaction substituted this... ie-if he was attacked, he would seek revenge, as it was the logical thing for him to do... for a while he mistook that for anger and feelings of vengeance, but it took his face-off with Espi to make him realise that he had been fooling himself... and to make him actually feel fear...
Since that day he has been tormented by thoughts of his bluepill family, plagued with his memories... love, family, friendship... that is what has led him into the arms of the Masked
He sees violence as a way to make him feel even more... and he needs that feeling to remind him of what he's fighting for, which is a return to normality through reinsertion...
However as his emotions rebuild themselves... he is becoming more and more capable of the whole emotive spectrum... whether things such as guilt, remorse or conscience will creep in remains to be seen.