I think this is just one of those things. From what i just Googled it seems to vary by writer...
- Hulk seemed to need oxygen in Bendis' Avengers Assemble story.- Hulk remained underwater for a week at the end of Fear Itself.
- Hulk passed out as soon as his suits oxygen supply broke down in Waid's run
- Hulk expressed the thought that he would eventually die in space in Aaron's run
- Hickman had Hulk operating in space with no oxygen and no concern in Infinity. He also showed Banner discard his oxygen device before transforming into the Hulk earlier in his Avengers run.
No biggie. This debate hardly hinges on this one fact. Interesting, though...!
Man Thing vs Marvel Super Zombie is a good showing of power. The Marvel Zombie Virus was transformed into a storm cloud that disintegrated any living matter with its rain. it also was able to turn 3 super beings into one super zombie. This cloud was so powerful that Hell Lord Hellstrom did not want to **** with it. Man Thing regen not only instantly regen any damage to him, but he also resisted the Marvel Zombie virus that claimed Wolverine, Silver Surfer, and Sentry!
http://www.comicvine.com/images/1300-3534962
http://www.comicvine.com/images/1300-3534963
http://www.comicvine.com/images/1300-3534964
http://www.comicvine.com/images/1300-3534965
As long Manthing could touch the ground, he was impervious. Then when destroyed he resurrected himself any way. Add to this he was able to use Empathy to force the Marvel Zombie Virus to feel fear for the Burning touch!
Man Thing fights Hell Lord Thog in a battle of collapse infinity. Beats Thog with Burning Touch.
http://www.comicvine.com/images/1300-3534984
http://www.comicvine.com/images/1300-2963715
Man Thing takes down D'Spayre. A fear lord. Take note that in this feat, Man thing was forced by D'Spayre to feel fear, yet survives his own touch!
http://www.comicvine.com/images/1300-2963712
Man Thing Burning Touch wrecks King Hyperion!
http://www.comicvine.com/images/1300-3202889
Man Thing can also cover a area with Burning Touch plants/Spores too.
http://static.comicvine.com/api/image/original/2937905-man_thing_ability_burning_touch_thru_plants__1_.jpg
http://static.comicvine.com/api/image/original/2937906-man_thing_ability_burning_touch_thru_plants__2_.jpg
http://static.comicvine.com/api/image/original/2937907-man_thing_ability_burning_touch_thru_plants__3_.jpg
Man Thing simply is too much.