I know I saw that very same pic long ago, it seemed like PIS. You know when the writers decide that something would be a good way of telling a story, and make the underdog more than what they usually are? Kinda like Hulk taking several blasts from Galactus and continuing to go after him. Thanos is also a powerful mystic, so perhaps that also helped out against Galactus. On the Astral Plane I have seen many crazy things as far as feats to say that Thanos would not have a hard time if Xavier attacked him, let alone Shadow King in his later form. Thanos may win but this is highly arguable.
