The heroes of Earth-616 have saved their home planet countless times but they still represent an existential threat to all mankind. Given the miracles, dark and otherwise, that Earth's civilians have seen heroes like Reed Richards and the Sub-Mariner perform, it's amazing that Marvel superheroes are as popular with the little people as they are.
Source:https://www.cbr.com/superheroes-marvel-comics-could-destroy-world/