Just because Integra is not considered a badass or powerful inhuman creature, does not mean she is not an excellent leader. Try to put yourself in her shoes. She's spent the entirety of her life being head of a successful organization and training how to kill monsters and protect herself, years of fencing and gun targeting as well as her home studies which ultimately meant her childhood died long ago. She dealt with the ridicule of the other male members of the round table. Towards the end of her life, she had lost everything that was of value to her, her home and all those considered her loved ones with the exception of Seras. She has the characteristics of an great leader; bravery, self sacrifice, compassion, determination, hope and the strength of the human soul itself. The fact that the most powerful vampire of all time not only served her family out of spite of their blood contract but respect should be saying a lot because everyone around her saw that same persistent Hellsing fire in her and they knew, even if she were hanging onto the last thread of her life, she would not stop towards her goals. This is another reason why Alucard's apparel also mocks that of the late Professor Van Helsing because he was the only human to subdue him and he saw this potential in his granddaughter. She is representative of all the qualities of the human race, whether they be good or bad, and a military leader who would fight and die for the benefit of her country and innocent lives. It is because of this that her voice carries in itself it's own unique power; to command, this is why her servants are so loyal and they would risk themselves to protect their one true beacon of light. She may not be what you consider a 'badass' but she in the least is one of the most influential and admirous female rolemodels. In the end, she was still the one to defeat the Major because she knew it was her duty and responsibility. No one else could have defeated him while retaining their honor and avenging the deaths of all those who died for her cause. She is fearless and she doesn't give a shit who challenges her for being a mere human woman and she has been that way even before the arrival of her 'pets'. It is because of this underestimation that her foes will always lose.

I just can't see why anyone would undermine her. Just because she lacks super abilities doesn't mean she's any less of an badass. It takes authority and respect to be a badass!