Wich Parralax? His most powerful incarnation ownz anybody else.
After him, I would go to Thanos, who have enough power to actually hurt Galactus. And eats Heralds lvler for breakfest, beating Surfer in one page (4 or 5 pannels). His technologies are powerful, and, with enough prep, could with no doubt be the most powerful out there.
Darkseid, with his herald lvler physical abilities, plus his cunning and his Omega Force is third. A dangerous and bad mother****er. Have beaten the JLA a lots of time. It's a herald lvler buster too.
After him, I would go with The Surfer. With his recent upgrad, he kicks ass. He define the Herald Lvler class.
Warlock, who is hella powerfull to, would comme 5th in this list.