This suit goes to show just how far Stark has come, and is a far cry from what he was able to achieve later on. Take note of the highly vulnerable eyeslits on the helmet and the lack of computer. The Mark I was completely mechanical and had no digital interface. Regardless, it did the most important job of all the Iron Man armors: it saved Tony Stark and changed his life.
The Mark V first appeared in Iron Man 2 and marks the first time that an Iron Man suit became portable. For those who missed that movie, the Mark V fit in a suitcase (or rather, it is the suitcase). This made Tony Stark's life a lot easier since from this point on, as he was able to become Iron Man anywhere
We all know that Pepper Potts is Stark's soulmate in the MCU. They've been together through thick and thin. One could wonder why Stark never made her any Iron Man armor (even for emergency protective purposes) before. This gets rectified in Avengers: Endgame, when Tony gave Pepper her very own Iron Man suit as an anniversary gift. It's called the Rescue Armor Model 1 or MK 1616. Fun fact: 1616, when converted into letters, spells "PP," Pepper Potts' initials.
The JRXL-1000 Variable Threat Response Battle Suit is also known as the War Machine Armor Mark I. While it belongs to Stark's best friend Col. James Rhodes, it's actually a stolen Iron Man Mark II armor. Upon bringing it to the U.S. military and another weapons manufacturer, it was outfitted with better armor and conventional weapons.
As it turns out, there is no limit to what Tony Stark can do with engineering. The Hulkbuster is proof of that, demonstrating that even something as destructive as the Hulk also has its synthetic match. It first appeared in Avengers: Age of Ultron.
Stark's lfinal Iron Man suit is the Mark LXXXV or the 85th Iron Man suit featured in Avengers: Endgame. It appears to be a more metallic and bulkier version of the Mark L. What does set it apart from the Mark L (aside from appearance and upgrades) is the fact that it was also built to control and withstand the Infinity Stones. It's basically a portable Infinity Gauntlet-- the pinnacle of Stark's engineering.
Speaking of Iron Man armors in Infinity War, Tony Stark also does not shy away from upgrades. His Mark L or 50th Iron Man armor featured a huge step-up in technology over any other suit he made prior. Instead of the clunky and cumbersome armor plates, the Mark L uses nanites or nanoparticles which can deploy all over Stark's body and manifest into an Iron Man suit. This makes it similar to Black Panther's suit.
The Mark III is the first official serviceable Iron Man suit, which was built as a labor of love in an engineering lab (Tony's garage). It can fly, withstand high altitude, and has enough weapons to make whole armies drool. It was also the first suit to adopt the gold and red color schemes faithful to the comic book Iron Man.
It wasn't until Iron Man 3 that Tony was able to create a prototype of one of his most portable Iron Man armors. The Mark XLII or the 42nd Iron Man armor is an experimental wonder, whose problems were *ahem* ironed out throughout the third movie.
It's worth noting that it wasn't Stark who built the Hulkbuster 2.0. The Mark XLIX was a modified Hulkbuster courtesy of Wakanda and Bruce Banner. Like the original Hulkbuster, it also fared exceptionally well. With it, Banner was able to defeat and kill Cull Obsidian, who was Thanos' most physically powerful minion.