It's hard to say. Deadpool has his regenerative power which gives him an edge in a long - drawn fight. He can keep coming back no matter how much damage he takes.
Well, they might start off by fighting each other. Deadpool with his unpredictable and crazy fighting style and Deathstroke with his highly trained combat skills. It could be a really intense battle.
Deadpool is the central character, no doubt. But in the first series, there are others. Besides Cable and Weasel, there are villains like Ajax. Ajax has a history with Deadpool and is part of what drives some of the early storylines. There are also some minor characters like Blind Al, who is Deadpool's roommate in a way. She adds an interesting dynamic to Deadpool's living situation and his overall story.
The very first Deadpool comic was 'The New Mutants #98'. This issue marked the beginning of Deadpool's presence in the comic world, laying the foundation for his unique and popular storylines.