Man, you hit on a fantastic dynamic. It's more than just a tough guy standing around; the tension comes from a reversal where the person being protected is already formidable. The bodyguard isn't there to save a damsel, but to manage a strategic asset who might run headfirst into danger. This setup lets the power balance shift constantly.
A classic for me is 'The Bodyguard' by Katherine Center. Hannah isn't a fighter, but her emotional resilience and professional competence as an executive protection agent make her a strong lead. Her client, a movie star, initially seems like a typical celebrity, but his vulnerabilities and her rigid professionalism create a fascinating push-pull. The strength here is in emotional armor versus physical.
Then you have the paranormal take, like in the 'Night Huntress' series by Jeaniene Frost. Cat is a half-vampire monster hunter, and Bones is the centuries-old vampire who becomes her protector and trainer. He's arguably more powerful, but her sheer stubborn will and evolving power constantly challenge that dynamic. Their battles are as much verbal sparring as they are physical fights against external threats.
For a real twist on the 'protector' role, 'The Kingmaker' by Kennedy Ryan fits. Maxim Cade is a security specialist hired to protect Lennix, an environmental activist. Her strength is in her convictions and her voice, his is in operational skill. The conflict arises when his duty to keep her safe clashes with her mission to put herself on the line. The protector becomes someone who has to learn to protect her right to fight, not just her physical body.
I find I'm drawn to stories where the 'protection' evolves into partnership. When the bodyguard stops just saying 'stay behind me' and starts saying 'tell me the plan,' that's the good stuff. The best ones make the safe house feel like a war room where they're equals plotting the next move.