Conditions they both have lightsabor they are on earth in the amazon and it's till death
@nando1313: Theoretically Deathstroke shouldn't be able to master it because he isn't a force user. It's actually dangerous to handle a lightsaber without proper training. He'd cut himself in half.
I don't doubt his skill, but Yoda is one of the most powerful Jedi of all time. He could move faster than Deathstroke could see and cut him into 20 pieces before he could blink. And when I say that I'm being literal. He could also just incapacitate him using the force.