Deadpool. And that's because of his healing factor. Sure, deathstroke has one too, but it's no where near as good as deadpools. Deadpool can regenerate from a skeleton. I've never even seen deathstroke regrow a limb, but correct me if i'm wrong. Even if deathstroke is faster and stronger and smarter than deadpool, eventually(even if the fight literally lasts days or even weeks) deathstroke will succumb to exhaustion. It's very hard to wear him out, but it is possible. Plus, deathsroke will have a very hard time dealing with deadpools teleportation. Deathstroke can run out of ammo and weapons, but deadpool has a magic satchel full of unlimited weapons and ammunition. And deadpool isn't as dumb as people think. He may not be as smart as deathstroke, but he's a briliant tactician and strategists. He once took out the entire marvel universe. That includes Ironman and Mister Fantastic. So even with prep, it doesn't change much.