Sci-Fi

The Matador Series by Steve Perry.

Dude is a soldier for an imperialist government, is out putting down a rebellion and has a borderline religious experience on the battlefield, puts down his gun and walks away.

He falls in with a religious teacher and masters a martial art called "The 97 Steps" which is part fighting style, part kata, part exercise.

He then gets with a shooting instructor who teaches him a very specialized non-lethal weapon that glues to the back of your hand. You fire it by pointing your finger and tapping your fingernail to the bottom of the barrel.

The darts that it shoots range from stingers, that hurt but do no damage. To shock-tox which incapacitates. To Spasm, which makes every muscle in the body hyper contract for 6 months.

He sets up shop as a bar owner on a military run planet and starts a one-man revolution every night with stolen dart guns and Spasm darts.

Overall, I think it's a 10 book series? Something like that. There are a couple of unrelated books set in the same universe

This is the base trilogy: