He's the guy deadpool was based off of. Deathstroke is a lot more serious than Deadpool is as arguable deadlier and also has a healing factor(Not a crazy fast one like deadpool though). Deadpool was made to Parody all the tragic anti heroes like the Punisher and Deathstroke and stuffs so they used Deathstroke as a base for (At the time) he was being used as a generic gun for higher in the comics.
His name is Slade Wilson. He's a super human with a Healing factor.
Just like how deadpool is Wade Wilson. A super human with a crazy healing factor.
Dat Zenstroke though... now that's badass! do you often lurk to /co/ Exaxuxer?
SHENPOOL: I feel a deep dark WORMTH!!!!!!!!!!
CATPOOL: it's probably that lazer beam in your chest
ZEDSTROKE: that dumb ass is dead