Collosus can't produce enough strength to hurt Ultron. Doom could wait until Ultron was done and then probably deactivate him via some small incantation. Ultron was created by Henry Pym with a deactivation switch in the back of his neck. Later version of Ultron have defense mechanism against it, I doubt it has any defense vs magic though. Iron man might have a chance at disabling him, but he'd probably need the suport of the Avengers to do it.
......Collosus is no push over. considering Ultron, It depends on which version, cuz hes got hundreds, and lots have seen official comic time. Are we speaking regular titanium based ultron? or Superpowered kill everyone and everything Immitaion Adamantium Ultron?(I stress Imitation Adamantium, not real adamantium) Doesn't matter, Collosus wins. Iron man gets beat cuz hed b worn out after helping deal with ultron and doom. doom is clever but would underestimate the mutant man of steel. Ultron would be seen for his strength and dealt with immidiately. Iron man would loose to Collosus, Doom would fail to hurt Collosus and start peeing in his armor once he figures out that magic has no affect on collosus either.......and Collosus makes a tasty cereal out of Van Doom called Dr. Crunch
Collosus: "MMmm mm mm. Good old crunchy scrap metal in little crunchy bites.....and look, it even has red scrap berries too!!......oh......thats his flesh...and blood...mixed in scrap metal......(GaaG!!!) awww man, I thought he was a robot like the other evil guy. (Only an idiot cudn't figure out Tony Stark is Iron man....I'm not that dumb.)"
Beyonder:"Colossus dies immediately."
LOL Beyonder must really hate my guts.
........LOL first of all the time periods need to be astablished, because I don't know much about the new Dr. Doom, but the old one always used traps and preplanned thinking to wreak havoc. by himself he is a formidable opponent, but not unbeatable, and he isn't even that strong, no where near 100 class. and his weapons aren't that deadly, he is a thinker and uses science and magic tricks, not a 100 class brawler.
and again, which ultron is it?
Ultimate Iron man was quickly trashed by Ultimate Collosus mind you.
I would think Ultron wud be his only major challenge
It is safe to assume that it is "fake adamantium ultron (although at once he was completely 100% adamantium.)" And I think that you have forgotten to consider that out of the four opponents Collosus is by far outclassed in the intellegence department. He's completely outclassed here, and if anyone wanted to bring up "ultimate" versions of characters they would have posted so.
You severely underestimate Doctor Doom. It is obvious you know little to nothing about the character.
Ummm, are you going by those off Marvel stats? Doom is way above in the tech area than Stark, and Stark knows it. And Doom's base armor has just as much firepower as his, if not more. Not the variety that Iron Man has, but as much firepower nonetheless. And, don't forget that it's enough to take on most cosmic beings.