First things first: Iron Man (in whatever armor) simply doesn't belong here. He is so vastly outmatched it is not even funny.
Remember Parallax is a guy who could destroy a universe (not a planet, not a solar system, not even a galaxy .....a universe) ....and then restart it in his own image.
Iron man in any armor cannot even destroy a continent let alone a universe, yet he is present here?
As for the others ....well, Sentry is The Man, and Rune King Thor is amazingly powerful (although he is used like some sort of magic wand .....just say 'Rune King Thor' and suddenly any one facing him automatically has to lose). All the same they are exceedingly powerful, with RKT able to pull off some crazy feats, and Sentry able to do things that (were he in DC instead of Marvel) would definitely belong in the Pre-Crisis era.
Nontheless Parallax wins.
He operates at a vastly different power level.
The only way he would lose is through some really stupid writing ....like what DC did when they had him lose, with GA even shooting off an arrow! Come on! That would be as silly as Wolverine putting down Thanos with his claws (hmmmm ....I remember Marvel having the clawed one slash Thanos), or Jubilee taking out the Dark Phoenix.
All things considered Parallax wins.