In comics it all started with shield
So the agents of shield can be considered as earliest character

It all started with Fantastic four’s human torch

Namor is the first Marvel Supehero. He made his debut in marvel comics in April 1927. He was created by the legend himself, Bill Everett.

according to comics the Marvels first superhero was human torch and later on fantastic four

in the comics, the first marvel superhero is the human torch and the anti hero is Namor