How did Captain Marvel die?

Answer 1

If you're talking about the Captain Marvel who died in the 'Death Of Captain Marvel' graphic novel(there are a few others, even within the Marvel Comics company itself), then the man who Captain Marvel acquired cancer from was called Nitro.

Nitro had the ability to cause explosions(or something like that), and Captain Marvel developed cancer from his repeated exposure to him through their constant battles through the years.

However, this may have led to the circumstances which caused his death, but I wouldn't outright say that "Nitro killed Captain Marvel" in such a deliberate manner...realistically, Nitro didn't up and *decide* to "give" Captain Marvel cancer, it was just a by-product of things that happened.

Answer 2

It was revealed in the graphic novel "The Death of Captain Marvel"- Marvel's first graphic novel. He contracted a cancer that was inoperable. Then he died surrounded by all of his friends and even some enemies that respected him.

Answer 3

Captain Marvel has died multiple times in the comics due to various reasons, such as sacrificing herself to save others or being killed by enemies in battle. Each storyline may have a different explanation for her death.