What is said of Slytherins born under all other signs is doubly true of Slytherins born under Scorpio. (Or was it that what is said of Scorpios is doubly true of Scorpios sorted into Slytherin?) There is no middle ground here - these wizards can embody all that is the very best in the world… or all that is the very worst. They are heroes, or they are villains. They are attracted to the dark, twisted, and forbidden mysteries of the world from the day they are born, and only they can determine whether they will study the dark arts in order to oppose them, or to embrace them. However, as Scorpio is a sign of transformation and regeneration, it is not impossible for even the most evil of dark wizards to turn to the path of good… Scorpio Slytherins have uncanny wisdom, insight into human psychology, and high “emotional IQ’s.” They are incredibly ambitious, often exist in a state of total ego, and if misused or hurt, can nurse the wound and seethe for decades. Still, although they are often tempted to do horrible things in the name of glory or discovery, they nevertheless are often the kindest, most compassionate, and most forgiving people of all, for they have seen their own inner darkness, faced it, and do not run from it when they encounter it in others.
Source: Harry Potter astrology.