4. The Inner Wolf.
Harry bitten by a werewolf (Remus so that he becomes his sire?) but because of his magic or maybe his acceptation of the 'curse' as it is given (Remus is captured and Harry goes to save him but when he arrives there he stands eye to eye with a wild werewolf and is attacked but accepts that its not Remus's fault and that its not the end of the world) or a combination makes him a Lycan. He gets wolf treats in his appearance, amber streaks in his eyes or the parts that makes his pupils round become dark amber so that when the light hits the eyes just right they seem almond shaped and very feral, enhanced hearing/sight/smell/strength/speed/endurance, rounded or pointed shaped ears, sharp nails/claw like, muscled/toned body and more hair. Besides that his instincts are strong (when challenged, when caged). He can change at will to his wolf form and on the full moon he can retain his human appearance but he looks very feral, has a wolf tail and his instincts are very strong so he is more wolf than man. He is the lord and master of the wolf kind.
He can also change in to the Lord and Master of the Wolf kind because he has two very magical substances in his blood (basilisk venom and phoenix tears) and his blood is even without that a magical substance (and because he is powerful, his blood is too...). One of these factors or a combination of 2 or all would be powerful enough to change the curse.