There's no denying that the reveal of the Hulk Buster Iron Man armor for Avengers: Age of Ultron has fans of the series excited. We are talking about a piece of machinery that was able to stalemate Hulk one on one! That's a pinnacle of fictitious achievement! Especially when you realize Tony Stark has had far less success with other "buster" suits he's created in the past. The following is a look at said suits as well as one match-up that he definitely should have lost, but by some miracle didn't.
THORBUSTER: Model 23
First Appearance: Iron Man Volume 3 64
After a sticky political situation leaves Asgardian worshippers dead in Slokovia, Thor and Asgard moved above the nation to collect the dead and seek revenge. At this point Thor was in control of his father's Odin Force so had even more power than before, making him a formidable opponent. Luckily for Earth dwellers, Thor had given Stark an Asgardian crystal for the world to use as an alternative and green energy source.
Using his brilliance, Stark created a new suit that ran on magical energy. The Thorbuster had experimental arm attachments for boosted punch power, could manipulate Asgardian energy, and made Stark impervious to damage. Or so he thought. Stark was able to stop Mjolnir mid-flight and easily fend off many other foes, but Thor destroyed it and Iron Man was ejected from the suit. Yep, the suit was impervious to all types of damage, except the one person it was named to beat. Thor eventually backed down after he dented Captain America's shield and realized he was attacking his own friends.
Anti Transformer Model: Version 1
First Appearance: New Avengers Tranformers Vol 1.1
The exact summary of this comic reads "Tony Stark created this suit after hearing rumors of Giant Robots...". I wish I had that kind of money to drop on projects based only on rumors! The rumors pan out and Stark travels to Latveria and engages in battle with the Decipticons! The suit does really well, but seeing as the rumors were a little late getting to Stark the suit was not completed and suffered from extensive power usage and was easily overloaded. Ultimately, the Anti Transformer Model met its end when Megatron beheaded the suit. Iron Man was okay of course, but his ego was likely shattered.
Anti Magneto Suit
First Appearance: AvX Issue 5
Successful? Yes, Surprisingly.
The one fight you think would be a walk in the park for Magneto, Iron Man wins. His name has a basic metal in it! How could he possibly lose? Despite the tease frame above that was released prior to the actual issue, it wasn't through Tony Stark's force of will. He was able to develop a suit made of Carbon Nanofibers. How Magneto wasn't able to effect any of Iron Man's circuitry at the very least was beyond me. All the times he's created "anti x" armor, and this is the one time it doesn't blow up in his face? Oh yeah, I forgot the time he did actually beat Magneto in his regular suit by pushing him down an industrial pipe vent. This is actually the only successful suit on the list, but it shouldn't be because MAGNETO IS A MASTER OF MAGNETISM! Old school Iron Man could and should have had his shrapnel'd heart ripped out by old school Magneto. End of story.
Phoenix Killer Armor
First Appearance: AvX #5
Successful? Made Things Worse.
Apparently the battle with Magneto was so short Iron Man had time to create another suit to destroy Phoenix, the most volatile mutant in the world.. This suit was designed to disrupt and kill Phoenix to keep the entity from traveling to Earth. When Stark fired the disruptor it fractioned the power of Phoenix and gave it to Colossus, Cyclops, Emma Frost, and Namor. And Magik. Great going, Tony. You managed to defeat a mutant with a power that is specifically designed for your downfall but you make a gaggle of mutants stronger trying to destroy one. I can't decide if that's better or worse than being defeated by someone whose primary attributes can be manipulated by your powers...