Onslaught by a mile.
Onslaught took everybody on, from Thor on down. only got busted up (in his final form with Franklin and Nate) by mindless hulk but then required all the heroes to be truly expunged.
Hulk could have broken the world and destroyed all the heroes he faced off against but... he didn't take them all on like Onslaught did.
Originally posted by Kid Kurdy
Onslaught was in fact skyfather level. WWH wasn't.
Hulk has the strength and energies to hang with Skyfathers, but he lack versatility and magical powers.