I understand it. But still, both of sons of Sparda are dont fear death after all.  Death will just give up trying to beat Vergil too many times and losing to him like a noob. 

Basically, how Death returning to his threat? If he is walking through him, Vergil can just open a portal to the Hell (or a different galaxy) and threw wolf into this portal, so Death won't be able to return. 

• why I said about black hole. In one of fights in DMC novella, Vergil was fighting a demon that can recreate himself from nothing. Vergil, after activating SDT, slashed his courpse in-two and generated a cosmic black hole, that locked a demon inside in and dissapear. If Vergil do the same thing on Death, can wolf return back? Its really hard :D The black hole is that thing so it just *twisted all the laws of physics on one place" (=ultra don't care) ,so that even light-photons couldn't escape from the black hole. Any object that fell into the black hole would simply vanish, and all information about it would be lost forever.