Traitor to a teacher, organization or tradition is also the best student or practitioner.
"The best of all would be the strongest student, yes? Wisest? Most learned in the ways of the Force? Best of all, Dooku would be! Our greatest student! Our greatest failure." ―Yoda Most bad guys don't start out bad. People can turn for many reasons, and it can happen to anyone, even those with the humblest beginnings. But those who turn their backs on their teachers, their traditions, or fellow followers of their calling have a conspicuous tendency to also be the best and brightest at what they do. There is some logic to this; it makes sense that the people who willingly break away from cohesive groups would tend to be particularly self assured, and in any case a premier pupil or top general who walks out on their side will attract much more attention than a lower level traitor. However, there are also more dramatic reasons for this tendency. A traitor who is more formidable than their former associates poses a much more credible threat than one who is less so, and the more valuable a person's contributions to a cause, the greater the pathos in their betrayal. A Top Tier Traitor is likely to possess The Gift. If the group they left is the one to which the protagonist belongs, they are likely to be an Evil Counterpart.