Possibly the most powerful Avenger ever died shortly after gaining his powers, but now that the X-Men are resurrecting humans there is no reason he can't return to the Marvel Universe. Dennis Sykes, also known as Flux, died not long after saving the galaxy from one of Marvel's largest characters, making his time as an Avenger an important but minuscule blip in the history of Earth's Mightiest Heroes.
https://screenrant.com/most-powerful-avenger-flux-resurrection-xmen/