Kayn is obsessed w surpassing Zed, he wants to outdo his expectations, be better than he could ever imagine, but nothing he does will ever be enough. Kayn could ascend to godhood and never feel that he's surpassed Zed.
He will only feel equal to Zed when he saves someone as helpless as Kayn once was, when he helps them past their circumstances so that they can become a person as capable as Kayn has become.