So GreenScar is on his way back to Earth and he runs into Thor who is also on his way back.
They get really drunk and Thor bets Mjolnir on an arm-wrestling contest. Hulk beats him and picks up Mjolnir (he is now worthy b/c he beat Thor and because of all the good stuff he did in PlantHulk).
Odin sees this and gives Hulk complete knowledge of how to use the hammer (lets assume he's really drunk too).
Hulk makes it to Earth without anybody noticing.
(Also Strange is tottaly pissed about CivilWar and decides not to interfere. He'll also be holding back the ridiculously powerful magic users but not interfering in any other way)
So now that Hulk is armed with Mjolnir and full knowledge of its powers, a good level of intelligence like we've seen in PlanetHulk and doesn't have Strange to stand in his way how long will his rampage last or is MarvelEarth completely screwed?
THE WAR STARTS IN THE BAXTER BUILDING
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Graffiti outside Latin class.
Sed quis custodiet ipsos custodes?
A juvenal prank.
Gender: Male Location: Hiding from The Doctor, shhhh.....
Uh oh......this could get ugly. there's only a few guys that can stop him. Sentry, other mages, warpers, Apoc, Reed with prep, and I think that's it. He'll cause alot of destruction before he goes down .
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nah, after the initial impact of Hulk's rampage, Doom creates a bunch of devices to suck all the gamma radiation out of hulk.
he then waits for the Fantastic Four to take on The Hulk, while he sneakily drains him. Hulk throws the hammer so fast that it breaches lightspeed and travels four years back in time, where it smacks Wolverine in the face (leading to his death).
thus Hulk is turned into Banner and Mjolnir is removed from him
To bad BB is too pissed off at the American government for stealing his mood gems , thus the planets only hope lies in the hands of a skitso superman.
Unfortunately Hulk DOESN'T get all nampy pamby in Sentries Aura and rams Mjolnir where the son doesn't shine , before making a throne out of the Things corpse.
Behold , King Hulk the first !
Be in awe at his control over the colonies, wonder at his might super-harem , and be frightened at the fact that the guy can personally tear apart your army like it's tissue paper.
I think Reed & Doom could combine with Magneto to find a way to destroy The Hulk. that kinda brilliance would always overcome.
'realistically' though, The Hulk with Mjolnir and a decent brain would smash anybody on the planet. noone coming at him with a frontal attack would survive. only horrible plot devices such as magic or reality warping could defeat him straight up. else, it's gotta be a schemer's battle... build the technology to drain The Hulk (basically do what The Silver Surfer can do normally) and then a battle strategy (possibly involving a sacrifice - Thing ) for removing Mjolnir from the picture.