Deathstroke after a long fight. Deadpool is by no means a slouch in h2h (when he's actually trying and not being dumb) but Slade is among the best, also, given his SS serum, I'd put his physique above Deadpool's. DP's healing factor might catch Slade off guard at first, but as the fight goes on, he'll eventually take the kill.
Some feats (I would post more, but I'm in a hurry)
Durability: Tanking an explosion
Falling from great Height:
Him fighting Immortal Man who has a HF on par with Wade's:
Those are all New 52 Deathstroke feats, where he has an Nth Metal suit, that increases his durability, and other physicals. This battle is with Pre-new 52 Deathstroke.