Warning: contains spoilers for Iron Man #22!
Marvel's Iron Man is officially stronger than Captain Marvel, confirms the publisher in Iron Man #22. The Armored Avenger is known for his many powerful suits of amor and not necessarily his own fighting skills; without his suit, he is easily defeated. But with his most recent fight, Iron Man proves resilient as as he survives a deadly weapon that killed the powerful original Captain Marvel easily.
Iron Man is no stranger to near-death experiences. His first appearance in Tales of Suspense #39 almost ended in disaster when deadly shrapnel almost pierced his heart, killing him. Thankfully, he was able to survive due to Ho Yinsen and his skills as a surgeon. Iron Man would eventually go on to refine his simple, grey suit to create the more familiar red and gold armor known by fans today. But his armor's strength alone is not the only device that saves him from certain death.
In Iron Man #22, written by Christopher Cantwell with art by Angel Unzueta, Iron Man is attacked by the Titanium Man; the latter is on the payroll of Source, a massive arms dealing company. The Titanium Man, while defeated, has one last trick up his sleeve, and sprays Tony with a lethal dose of Compound 13 as his friend War Machine can only helplessly watch. "Compound 13 is the most lethal nerve gas ever studied," narrates War Machine as Iron Man falls to his knees. "Compound 13 killed Captain Marvel. A man who could fly through space on his own faster than the speed of light."
Compound 13 did indeed kill Captain Marvel - the original male version, not Carol Danvers - in a memorable story that stretched out over years. Captain Marvel encountered the gas in Captain Marvel #34, and though Compound 13 didn't kill him outright, his entire body combated the gas for years. Unfortunately, the gas induced a carcinogenic growth in his body that could not be cured, and Mar-Vell eventually died in The Death of Captain Marvel #1. While Iron Man does have a filtration system in his armor, it must be stronger than Mar-Vell's own body - since he could easily withstand most weapons and exposure to the vacuum of space.
This feat essentially makes Iron Man (and his armor) stronger than Captain Marvel, a being who has fought many invaders from space and even magic villains. The fact that his man-made filtration system is stronger than Mar-Vell's entire body also points to a potential confrontation between Tony Stark and the current Captain Marvel, Carol Danvers, being more than a one-sided fight. Unfortunately, Compound 13 took years to kill Captain Marvel, and so Iron Man may not be entirely out of danger yet; knowing the Armored Avenger's luck and track record, he could very well be sick without even knowing it.