Wanting power and control over things in your life is not an inherently bad thing. But the unscrupulous ways some characters go about this can devastate a relationship.
Assertiveness is fair, principled, disciplined, fighting. And it’s the kind of just self-advocacy coupled with mindful concern for the impact on others that defines healthy character.
Assertive behavior is a key element of healthy, independent, adult functioning. But because asserting oneself is a form of “fighting” for one’s legitimate needs, it’s easy to get confused about the difference between aggressive and assertive behavior.