Meltdown boom booms on Sphinx
Let me first get this out of the way, yes, Sphinx has a clear advantage in this match. And yes, he probably would win on any other day. But not today.
Meltdown has the ability to create plasma spheres that detonate on her command, these are very powerful. She also thanks to Pete Wisom is able to create "plasma spikes" that are as well very powerful. Sphinx in possession of the Ka Stone is able to channel mystical energies and emit them as powerful concussive, light and heat blasts. He also has Superhuman strenght and the ability to fly.
Meeting on the Blue Area of the Moon, the two meet up and quickly go into battle, Meltdown quickly throws out her plasma bombs and they explode in Sphinx's face. Hes very pwerful so hes only slightly stunned, she quickly moves again for another salvo and knocks him back a bit more. Sphinx retaliates with a heat blast that Meltdown dodges running up to him creates her plasma spikes and stabs him, to no avail as Sphinx is very resistant to physical harm. Sphinx flies being able to live without oxygen and begins to attack Meltdown from above with heat, light and concussive force blast. Meltdown is on the run dodging and weaving and she gets hit. Sphinx is able to swoop down and in time deliver a final blow, using all of the Ka Stone's pwer and meltdown dodges the final blast. With his energy depleted Meltdown renews her attacks not knowing his energies have been depleted. plasma bombs and spikes efficiently and quickly, Meltdown is able to bring him down and tire him out. Meltdown doesnt kill him but Sphinx is defeated.