A True Alpha is a canine werecreature who becomes an alpha solely by the strength of their character, their virtue and sheer willpower.
A True Alpha is the rarest kind of alpha, shrouded in myth and is said to appear once in a 100 years.
A werewolf cannot attain True Alpha status if they ever kill someone.
In Season 3, Scott McCall's eyes, during situations of high duress but sheer determination, briefly turn alpha red. In Currents, Alan Deaton confirms Scott has the potential to become a True Alpha.