Heres your simple Samurai cheese guide.

If you're not the Samurai, Don't attack them when Chiten is up. (the blue looking buff.) If the debuff from chiten is applied to you and you are about to get hit with that LB pop whatever shield abilities you have, and you may narrowly survive, assuming the SAM doesn't have a lot of battle high.

If you are the Samurai and your LB gauge is full...

Pop Meikyo Shisui. This gives you 3 seconds of no stuns. Make yourself a gigantic nuissance and go slap a caster or a healer around. If they're a catgirl, that's even better. You want to make them target you. Thats when you use chiten. When those unsuspecting fools attack you they will recieve a debuff. If you use your LB on that person, they will instantly die* (Assuming they don't have a dmg shield up, and you don't have any debuffs that reduce your damage.) Not only will they die, but other people around them with that debuff also die.