Writing a badass character while being, well, not-so-badass yourself? The 100 Deadly Skills books by Clint Emerson, a retired Navy SEAL, might help. The books are very entertaining read just for fun, but they're also fantastic for researching those secret agents/assassins/bounty hunters many of us genre types love to write. And it's not just the skills themselves that might come in useful, but the whole mindset of the "Violent Nomad," as Emerson puts it, can help you get into your protag's head and create a more realistic character.
100 Deadly Skills: The SEAL Operative's Guide to Eluding Pursuers, Evading Capture, and Surviving Any Dangrerous Situation is just than, a well-rounded look into what it means to be a Violent Nomad. The book is split into sections: Mission Prep, Infiltration, Infrastructure Development, Surveillance, Access, Collection, Operational Actions, Sanitisation, and Exflirtation and Escape. Need to know how to trick fingerprint scanning software, turn a newspaper into a weapon, or to make an improvised infrared light? Emerson's got your back.
Do you love Jackie Chan movies? Me too. That's why A Guide to Improvised Weaponry by Master Sergeant Terry Schappert, U.S. Army Special Forces, and Adam Slutsky caught my eye. No more boring action scenes, guys! Why not have your protag pick up a plunger or salad tongs instead of a gun? The scene practically writes itself.
In 100 Deadly Skills: Survival Edition: The SEAL Operative's Guide to Surviving in the Wild and Being Prepared for Any Disaster Emerson not only gives tips on how to survive a natural disaster or survive in the wild but also talks about defending your home, securing public spaces, and signaling for help. Here you'll learn how to escape a flooded vehicle and to survive a shark attack.
A word of warning: reading these might leave you feeling a bit jittery for a while and seeing danger everywhere. Hopefully you won't have to actually use most of these skills in real life, but hey, some of this stuff might come in handy sometime.
Now go write that action scene with the plunger. I know you want to!