Why would Hal even bother? Reminds me of the fight scene from Identity Crisis where Kyle, despite wearing the most powerful weapon in the universe goes hand to hand with Slade instead of clobbering him with a giant anvil from half a mile up. I've always found that dumb as hell.
Avatar: Here's to the late, great Steve Dillon. Best. Punisher. Artist. EVER!
Slade is the Batman of DC villains in that they love to grossly inflate his competence and danger factor, without the built in excuse that at least Batman has a long history of being a beloved and great character before it got out of control.
Beast Boy has been able to give him a run for his money in a solo match up. Almost any of the premiere JL characters should swat him aside with ridiculous ease. Hell, just looking at the Titans, so should Donna.