Tbh Deathstroke if you're going for a normal defeat rather than actually killing themselves. Deathstroke is much more smarter and knows how to play his cards easily, he took the justice league in a very unique way and could go toe-to-toe with batman. While deadpool is more wild and unpredictable, Deathstroke knows how to trick an opponent. On the other hand if the fight goes for extreme measures, deadpool takes the cake, while both have healing factors, as far as i know deadpool's seems to be more effective on that regard, plus despite his insane personality and way of approaching things is crazy that doesn't excuse him for being a powerful anti-hero.