Vile is actually a name that he insists on.

He insists on the name "Vile" since he despises his own powers, which allows him to alter his body in anyway, even making himself invulerable.

He despises his powers because they're too strong and he fears that he may end up being like his brother.

FYI, the japanese symbols on his gloves are as followed. His left hand reads "bad" and his right hand reads "heaven".

On the back of his coat they are both together reading out "bad heaven".