There are no good or bad signs: the Zodiac is impartial because it symbolically reflects the different qualities of being. In reality and particular social contexts, the zodiac signs take on values that only apparently reflect negative characteristics. The culture or particular circumstances push the individual to render these characteristics in a selfish, exclusive sense, to the disadvantage of others. In this sense, Scorpio, whose global function consists in transforming to be reborn and advance on the evolutionary plane, is experienced as an agent of destruction because selfishness limits the individual’s view, arresting them at the destructive phase, thus making them unable to transform themselves.
For example, the sign of Scorpio is associated with the surgical profession because the surgeon tries to restore organic functionality with a scalpel through the partial elimination or functional restoration of defective organs, allowing the patient to continue in his life course. But also, the one who stabs in a fight, perhaps an evil Scorpio, acts according to the same principle. The difference lies in the fact that the former exerts a curative action, the latter potentially deadly because limited by their instincts.
I have deliberately adopted extreme examples, but the concept is valid for all those Scorpio manifestations that replace the principle of transformation with the much more limited one of destruction.