Primal zerg power, though you better make tracks for all the death world parts of marvel earth like that place magneto went to that had the dinosaurs. Also do you get the powers of those you kill? If so I would suggest killing a bunch of villainous mutants or inhumans once you have gotten all you can from the natural world. From what I understand, the way primal zerg work is that what they kill they take essence from, then use that essence to give themselves traits from what they kill, ie kill a bird, get wings of the same type as the bird but upscaled to be useful to you, so 20-30m wingspan for a human.
One other big thing to note about primal zerg is that they change based on their environment and those changes stick, to the point that drowning yourself nets you gills, breaking bones makes them stronger, and at the high end gradually starving yourself in a dark room will eventually net yourself the ability to leech off of other dimensions or generate energy ex nihilo.
I would also suggest nomming a symbiote if you get the chance.