I disagree, when has Mario ever faced someone with "killer instinct"? He has faced kidnappers and walking bombs but none of which were true killers. Marv is a badass, we all know that, but he is a smart, sadistic, killer to boot. Giant Mario wouldn't be any bigger then normal sized Marv. Fireballs could hurt Marv, but I honestly believe Marv's tolerance for pain would allow for him to walk through the fire and take Mario down with him. And God forbid Marv gets his hand on Marios little plumber neck, he would snap it like a twig. Mario will likely go over, but Marv would kill Mario, no doubt in my mind.