Originally Posted by
rutog98
We are talking about mutants at the full range of their mutation being able to contend with the likes of Galactus. Storm and Davil Haller easily fit this category. Storm's powerset is to perceive the universe around her as patterns of energy she can bend to her will. She can observe how the universal forces around her work and replicate what she sees. Furthermore, she can feed on the life force of heavenly bodies and gain spiritual and material sustenance from them. This power, in turn, is limited only to by the strength of her will and body. She once displayed the strength of will to host Eternity, the embodiment of all matter and energy in the omniverse. There is no upper-limit to her willpower. So, the only thing limiting her power is her human body, which plenty of canon out there has clearly established is temporary if she chooses to work towards her full potential as she has the potential so transcend her humanity. We see this touched upon in the Roguestorm story arc, in the 12 story arc, and an earlier issue of X-Treme X-Men. So, given that she was able to host Eternity and can transcend her humanity, an argument can be made that Storm could actually dwarf Galactus and become an omniversal power.
Even at her current stage or evolution, we have seen Storm wield the full power of a galactic core (millions of stars and planets crammed into a relatively small area of space), she was able to defeat the Trion who were the sum of all matter, life, and energy for an entire reality's past, present, and future in combat as well as sew that reality back together again when it was unravelling at its seams. She's thrown attacks backed by the full power of stars, and more. These feats right here actually would justify her fighting a Galactus-level antagonist right now and winning...and it would not be PIS...and she is nowhere near her full potential either.
Legion was able to put an entire universe in a box. "Nuff said.
Regarding Selene, there is no upper limit to the amount of life force she can absorb from people. She demonstrated the ability to transcend her flesh and blood form and was able to start devouring the spirit realm (which is probably the Astral Plane). Given that her powerset includes magic, I believe she has the powerset to be able to take on somebody like Galactus if she devoured enough life force prior to the fight.