Superhero Iron Man is always looking for an edge in a fight. That's part of the reason why he keeps developing new suits of armor. Well, that and the never-ending obsession with technology that has consumed the vast majority of his adult life. But his search for any edge and every possible advancement would definitely lead him to the Pokémon, once he found out they existed. He would build a team perfectly complemented his own skills and abilities.
But he also takes the long view, and would also select Pokémon with impressive evolutionary options to work with.
10 Charmander
Everyone needs a starter Pokémon and Iron Man would definitely go with Charmander. First and foremost, the little orange guys are essentially adorable pet-sized dragons who breathe fire. When you stop and think about it, that's pretty sweet. But Iron Man would put the effort to evolve his Charmander all the way up to a Charizard. He would then have a full-sized dragon capable of flying and burning almost anything into rubble, one that's still all kinds of adorable. In a fiery death way, of course.
9 Mega Metagross
As the full evolution of a Beldum, the robotic Metagross is already quite powerful. But if you can get your hands on Metagrossite, you can still upgrade a Metagross a step further into Mega Metagross.
The Mega version of Metagross is constantly floating, and has multiple brains that allow it to process information at incredible speeds. On top of that, it has powerful psychic attacks in addition to its four sets of dangerous claws. You know Iron Man is going to find Metagrossite and make himself a Metagross.
8 Magnezone
When you spend a significant amount of your life flying around in an armored computer, keeping a magnetic Pokémon around seems like a bad idea. It's worth the risk for Magnezone. Once you've evolved a Magnemite into a Magneton, you can still take things a step further. When exposed to special magnetic fields, Magneton can then become Magnezone. They look like flying saucers, and do have the ability to fly. The same abilities that allow them to fly also allow them to carry things much larger than them through the air. All of this makes them a solid defensive player on a team, and a key roster to Iron Man's Pokémon crew.
7 Golurk
Classified as a Ground/Ghost-type Pokémon, Golurk has somewhat of a mysterious past. They are believed to have been created by an ancient civilization to serve as a laborer, and as protection for both people and other Pokémon.
They look a lot like a very large suit of armor, which is obviously going to appeal to Iron Man. Golurk can retract his arms and legs, then fly like a rocket. He can also take the form of a canon in a similar fashion. Everything about Golurk makes it a perfect sidekick for Iron Man.
6 Porygon-Z
Keeping in mind that they do still have a physical form, Porygon-Z is a man-made virtual Pokémon. While upgrades to its programming have made it a little erratic, it still has some strong moves as well as at least two that only Porygon-Z is capable of learning. But what would make this Pokémon appealing to Iron Man is the fact that it is virtual and programmable. Other researchers have had problems working with Porygon-Z because of how twitchy the little guy is but Tony Stark would find a way. It's actually kind of scary when you think of what he might be able to do with the little duck-like Pokémon.
5 Greninja
When you look at the types of Pokémon in Iron Man's roster, Greninja is exactly what he needs to fill it out. The Dark/Water-type Pokémon resembles a blue frog. He is incredibly fast and agile, allowing him to confuse his opponents in combat.
Greninja can attack using throwing stars made out of compressed water which do serious damage to almost anything and anyone. He can also be quite stealthy, giving him a high chance of getting the first shot in. That's what Iron Man wants on his team.
4 Snorlax
Every team needs a Hulk. Snorlax might not be a Hulk, but he could give the Green Goliath a run for his money in the raw power department. Generally speaking, Snorlax are found sleeping in ridiculous places or eating everything. Keeping in mind that they need to eat approximately 900 lbs of food a day to survive, you can often find one eating and sleeping at the exact same time. Their sloth-like ways are deceptive, though, as they're powerful and can unleash devastating attacks, often without moving from wherever they're sitting. It just gets worse if you can get your hands on a Gigantamax Snorlax. Iron Man would be simultaneously annoyed and excited by this one.
3 Eevee
If there's one thing that Iron Man loves, it's options. You just have to look at all of the different suits of armor he's made over the years. Many of those suits are only useful in very, very specific circumstances. Once he found out about all of the potential evolutions, he would have to catch one.
Honestly, Iron Man would probably go out his way to catch several of them and work his way through all eight evolutions. The potential for research and development with an Eevee would be too much for him to ignore.
2 Kyogre
When you want raw power on your team, try to find Kyogre. This whale-like Pokémon is one of the weather trio and has power over the element of water. With the Blue Orb, it becomes even more powerful and twice the size it already is as Primal Kyogre. This process isn't so much an evolution as it is an enhancement. While it is generally peaceful, Kyogre can do some serious damage when aggravated. A Pokémon the size and power of Kyogre is exactly what Iron Man will need when fighting the worst of the worst.
1 Mewtwo
Iron Man gets into a lot of fights with very powerful beings, some far more powerful than him. As such, it pays to have a Pokémon like Mewtwo at your side. Created through disturbing scientific research on Mew, Mewtwo is an incredibly powerful and rare Pokémon. Its psychic powers give it a series of abilities including telepathy, mind control, and flight. Because of its secretive nature and rarity, the full extent of Mewtwo's abilities might not be fully known. A pairing between Iron Man and Mewtwo would be beneficial for both sides. Iron Man gets a powerful ally and Mewtwo has someone it can work with that will treat it properly. Plus, Mewtwo also has Mega forms, which Iron Man would love.