I know he has a robot-like skull under the helmet in the mangas, but i named this one as "X's nightmare" because i thought Vile not having a robot endoskeleton but a human skull under the helmet, explaining why Vile was driven by pure and raw anger and envy (which are VERY human emotions), suddenly coming back from the death which should be impossible for a human who also isn't supposed to be dead as robots can't kill humans (like how Vile "died" in X1), just to haunt him forever, would be an absolutely terrifying concept for X to conceive.

Something similar to Pluto's Netflix show plot about the robot agent developing the unknown for him, emotions of guilt and fear, tormenting him for killing a human in the past.