Bad people can't be strong because the root of evil is self-deception, and a lack of general reason and fairness which are mental faculties required for intelligent thought and behavior.

The only reason why people think bad people are strong is because they don't understand them. They deceive you into thinking they're strong by patronizing, belittling, and lying about their true capabilities but evil people have to take advantage of weak individuals because a strong person wouldn't fall for their nonsense. You aren't strong if the only people who submit to you are low self-esteem delusional idiots.

And no, strong and capable people have infinite potential. All spirits possess infinite capabilities. Only fully righteous or good people are truly strong and are never willing to deceive and manipulate because you would have to deceive yourself and degrade your own mind and being to do so. Hypothetically if a good strong individual decided to become evil one day, it would require ignoring basic intelligence and they would become less competent in achieving their goals. Largely due to the fact that manipulation and deceit are dependent on people believing in it and falling for it. So they're relying on the incompetence of others to achieve their goals, and they also need to take advantage of them and use their vessels as well.

This also proves that they lack the self-sufficiency, competence, and skills to achieve their goals the right way on their own without trying to use others.