ANSWER:

He has committed a sin and he must seek the forgiveness of the one he had wronged. If he is not willing to forgive, he has no other option but to ask Allah with sincerity to forgive him and conceal his sins. 

If someone did extreme wrong to other person and this person does not want to forgive him at all.Whats the rulling of islam for the person who did wrong to other;he has to repent to Allah only or he has to ask forgiveness from the person also to whome he wronged.What if he only repent to Allah and do not ask forgiveness from human and this human always cursed him because of his wrong doing.