When it comes to Marvel's X-Men, casual deaths and resurrections were commonplace long before the Krakoa era ever began. This was especially true in the case of Jean Grey, who had originally died in the form of the evil Dark Phoenix. She would later make her way back to the land of the living, although this was thanks to a rather controversial retcon.
Source：https://www.cbr.com/x-men-jean-grey-power-girl-retcon-similar-dc-marvel/
