There is a thread at the X-Men forum about their system of industrialized resurrections. But then I thought, why don't we take a step back and talk about all the myriad ways characters can come back from the dead in the Marvel universe? And we do not mean excuses where a character was not really dead after all (his healing powers saved him, the scene was faked, it was someone else who died, etc), this is for characters who 100% kicked the bucket.
Some ways to do this, just the ones I remember right now.
* As said, the Krakoan way
* The Hand's resurrection spell (e.g. Punisher's wife)
* The "Green Door" (e.g. Hulk and other gamma-mutated)
* Take him from the past before death and bring him to the present (e.g. Scott Lang)
* Magically rescue him from the afterlife (e.g. Wonder Man)
* Death herself lets him go (e.g. Dr. Strange)
** Same for Hela, in the case of Asgardians
* Reality warping (e.g. half the universe)