From the old days Iron Man vs. Titantium Man. The battle starts at the end of one issue with Tony clearly facing a tough enemy, second issue of the fat has Tony struggling to survive against Titanium Man and it doesn't help his suit is missing a critical component. Happy Hogan gets a moment where he retrieves the piece and dashes for Iron Man only to be wounded. Then a furious Tony Stark vows to make sure Happy's avenged and spends the next issue curb stomping the Titanium Man.
Pretty much Demon In The Bottle on a meta level for tackling alcoholism realistically.
Not so meta is Iron Man taking on a dozen villains, most B and C listers, but still that's some tough odds.
Iron Man Vol. 1, #200. Stark is finally taking the fight to Obadiah Stane after so long being his drunken Butt Monkey. In the ensuing battle in the very corporate building that Stane stole from him, Iron Man is trapped in a room with Pepper Potts and Happy Hogan held unconscious. Stane comes on a comm screen and tells him that if he moves, motion sensors would detect it and send a killer surge of electricity to kill his hostages, which means Iron Man will be forced to starve to death rather than kill his friends. After an arrogant rant, Stane signs off with a smug farewell, certain of the horrible, lingering and inescapable death he has just condemned Stark to. Against this, Stark has only one thought, "Don't count me out, Stane," as he calmly uses his greatest advantage against Stane, his incredible inventive intelligence, as he calmly scans the room and finds a critical power conduit point within the firing arc of his chest piece's unibeam weapon, which is fired strictly by a neura-link and defeats the deathtrap and rescues the hostages in seconds.
Iron Man vol. 1, #259. The Living Laser - disguised as the ghost of the Titanium Man - has critically damaged a nuclear power plant... and Tony has about 70 seconds before it blows. So, he digs it out of the ground, lifts the entire structure, flies it out to sea, dumps it in the drink, digs it a half mile into the silt at the bottom and manages to get out of there seven seconds before it blows. As a feat of strength, it's not been matched by him yet. Throughout, he remains cool, calm and collected, as if it were no more than trying to get a leaky garbage bag out of an appartment without dripping on the carpet.
Iron Man vol. 1 #300. Not only does the Modular Armor debut, but so does the Iron Legion. Rhodey (War Machine), Michael O'Brien (the Guardsman), Bethany Cabe, Happy Hogan, Carl Walker (Force) and Eddie March (who was Iron Man briefly when Tony retired) take to the sky in armor to fight Ultimo.
During the "World's Most Wanted" arc, Tony manages to protect the identities of his fellow heroes and humiliate Norman Osborne, all while his brain is slowly destroyed and he goes backwards through his armors until he fights Osborne in his original. Let me repeat that: Tony Stark, near brain-death and in an armor which he admits was built in a cave (WITH A BOX OF SCRAPS!), takes on Norman Osborne, at the time the de facto head of the United States and wielding the most up-to-date repainted Iron Man suit. Naturally, Tony's terrible, but that's how he wins: by shaming Osborne in front of the media. Then he royally screws over Osborne while comatose by having Don Blake, a.k.a. The Mighty Thor appointed his doctor so that he won't have his life support terminated.
During the Dark Reign story arc, when Norman Osborn (dressed in Iron Man derivative 'Iron Patriot' armor) finally catches up with the near braindead Tony Stark, and proceeds to pummel him into the ground. And after deleting his brain, evading every government on the planet, reassembling every Iron Man suit he'd ever owned, and finally getting the snot knocked out of him, what does Tony have to say? "I win." Norman, you have just been pwn'd in the hardest of cores.
Another one from Dark Reign, Invincible Iron Man 17-18. Pepper Potts successfully infiltrates the H.A.M.M.E.R Helicarrier and frees Maria Hill and Black Widow by impersonating Madame Masque(wich tried to kill her and Tony and failed), I'm not usually fooled by gambits like this but this one got me by surprise, and it was AWESOME.
Jarvis tells Tony he can only carry four people with the suit after thirteen people had been sucked out of a breaking Air Force One plane. Iron Man then saves them all anyway, gives a little "yay team, yadda yadda yadda, whatever, I'm gonna go now" speech, and promptly flies into the path of semi and breaks into several pieces... before the scene flashes to Tony using remote controls to do all of this.
Iron Man 3 proves that the original build-a-suit-in-a-cave-with-a-box-of-scraps feat was not a fluke, and did not depend on terrorists with military-grade weaponry. Stranded in rural Tennessee, Tony builds a bunch of Improvised Weapons, with parts he bought at the local hardware store and some borrowed children's toys, in an auto mechanic's garage. A long-neglected garage, for that matter. And while the weapons he builds are not as effective armor as even the Mark 1, he did it in only a day.
Problem: it's Tony Stark, Jim Rhodes, and 40 or so suits of armor against all the bad guys. The armors can be piloted by Jarvis, but much less effectively than with a human inside them. Tony can just jump from armor to armor, but none of those are fitted for Rhodey. He has to get his own armor back for that. So he does. Even though it's suspended by cranes, over a Death Trap, with the President as hostage inside it, in the middle of a huge battle. Very Bad Ass.
Pepper fumbles and Does Not Know Her Own Strength in armor near the beginning, because it is one of her first times inside the armor, if not the very first. Presumably she's a fast learner, though, because once she has Extremis powers she can put them to good use and kill Killian herself.