Tony Stark's latest armor in Iron Man 3, the Mark 42 suit, was almost his best suit yet, but several factors led it to be rife with issues.

Tony Stark obsessively built new sets of armor in Iron Man 3, yet the Mark 42 suit, his magnum opus at the time, seemed weaker than his armors in previous MCU films. 2012’s The Avengers was a turning point for Tony Stark, putting him on a team with superpowered (or highly skilled) colleagues and having him face off against an army of aliens. Tony’s Iron Man 3 suits were meant to prepare him for any scenario, but he never completed work on his latest suit at the time, preventing it from being his most powerful armor yet.

Tony Stark’s near-death experience in The Avengers left him with lasting trauma, so he built thirty-five new suits by the events of Iron Man 3. Many of the suits were tailored for specific situations, providing Stark with armor for almost any occasion and a coping mechanism for his paranoia of greater threats coming to Earth. The Mark 42 armor combined the best elements of all previous suits and had the most robust suit-up method, assembling in pieces (each with their own flight system) around Stark.

Despite being what should have been his greatest armor yet, the Mark 42 repeatedly malfunctions throughout Iron Man 3. In addition to easily running out of power (impacting its performance in combat against AIM forces), the suit also repeatedly fell apart in response to powerful impacts, such as being hit by a truck. The Mark 42 appeared to be a far cry from Tony Stark’s earlier armors, but the fact that it was never finished was the only reason why it seemed so weak. As stated by JARVIS, the Mark 42 Iron Man armor was still in its prototype stage and was therefore not combat-ready. Regardless, Stark used the unfinished suit as his main armor throughout Iron Man 3 and detonated it by the end. While the suit struggled against three helicopters (which Stark would have effortlessly destroyed with previous armors), there were some moments in Iron Man 3 where its full potential was hinted at.

During Iron Man 3’s Air Force One sequence, Tony Stark used the Mark 42 at nearly full power, killing the Extremis-enhanced Eric Savin with a single blast from his uni-beam and handily rescuing all surviving passengers. The Mark 42 Iron Man suit had the most advanced offensive and defensive systems yet, but the fact that Stark never finished it left it with functionality and power supply issues that would have been resolved if it advanced past the prototype stage. Iron Man’s Mark 43 armor, shown throughout Avengers: Age of Ultron as a highly-efficient suit, provided a glimpse at the Mark 42’s potential if it’d been finished in Iron Man 3.

The Mark 42 was meant to be Tony Stark’s “perfect” armor in Iron Man 3, but his obsession with constantly making the next best suit and the appearance of The Mandarin (Aldrich Killian’s puppet) fittingly prevented him from truly perfecting the armor. It was only after Tony stopped obsessing that he successfully crafted the Mark 43, which shows no issues in battle against Hydra’s forces in Age of Ultron. If Tony Stark had completed work on the Mark 42 armor in Iron Man 3, however, it would have truly been his best suit in the film.

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