By the suit alone Iron Man, without being connected to an external power source, can lift in excess of 100 tons. He has survived ground zero of a nuclear explosion. He his weapons are powerful enough to injure actual gods and otherworld beings. His intellect and mechanical skills are such that he has completely taken over alien technology for his own use after only a brief contact with them.
Hell, he beat Magneto...who controls metal.
I'm sorry but Master Chief would be utterly destroyed by Iron Man. Tony could very easily hack and over ride Master Chiefs Armor since he doesn't need to be connected into a system like Cortana does. He would probably confine Cortana by playing Iron Maiden over the Chiefs com channel. He'd then power down the suit and gloat before punching MC into Orbit.
But let's say Iron Man left Master Chiefs suit alone. Master Chief has no weapons that could actually injure tony outside of possibly an over charged point blank spartan laser, which would probably only scar the armor. Iron Man is more durable, stronger, and faster then Master Chief.
Master Chief is brave and he is lucky, but he's also been fighting against advisories of at the very least average intelligence. Tony is one of the smartest people in the marvel universe. He's the Bat Man of Marvel.
--- I'm a Christian. I play Diablo 3 and one of my favorite video game characters is the Lich King from Warcraft. Deal with it.
Even in regular armor IronMan gives Hulk and Thor a decent run, MC would lose.
But then there's stuff like when Iron Man got smacked away like a gnat in his Hulkbuster armor, by the Hulk. And then when he got his ass kicked by Thor when Thor found out Iron Man made a clone of him.