yes, u’ve answered ur own Q. Allah forgives sins against Himself but its NOT the same if one sins against a human or a living thing [like torturing an animal]. u have to have that person’s forgiveness. here, i’m talking about major sins [gunaah e kabeera]. if a person does NOT forgive u then u’ve done ur job. Allah might forgive u and reward him equally to make him happy. so Allah’s mercy is endless. Allah is JUST!**