I don’t think people understand how broking Viltrumite are. The only reason they aren’t demolishing everyone on sight is because the writers want to make a good story. They have smart atoms which allows them to add mass and energy to their bodies, and because of the smart atoms their bodies are highly efficient. Since they are able to add more mass and energy to their being this will allow them to litteraly become stronger when they want to. Like saiyans with their transformation increasing their ki which turn in makes them stronger or like energy absorbing beings for example sliver surfer, star fire, Gwen Tennyson, and of course supermen and by adding energy to a particular body part like eyes it will give enhanced vision. With their DNA it is possible for the child to inherit the other parents powers without their DNA being overwriting, because of their DNA ability to adapt and self-repair. Oliver Grayson is example even though he has Viltrumite blood the compatibility wasn’t good. To conclude because of their smart atoms the potential for Viltrumite is endless. By the way only reason mark and thragg were starting to burn alive because they where over taxing their smart atoms, since it was trying to protect them from the sun but also make sure they are efficient in the fight. It like trying to walk as throw a football at pretty far distances or it like fighting underwater your body is working hard to make sure you have oxygen and the energy to throw a punch. By the way you have to scroll down to see the images from the hand guide in the link I sent. The hand guide is called: The Official Handbook of the Invincible Universe. kryptonians powers are based on the sun so mark and thraggs feat is incredible and also as they fought they went deeperrrr inside the sun 😱.