*Sigh*
I'm not even going to try and argue...The fact of the matter is that at a close proximity, nuclear fallout kills EVERYTHING, and I mean EVERYTHING.
Dante is NOT immortal, far from it infact, it's simple logic that something with as much destructive and harmful power as a nuke could easily kill him, because, nuclear radiation actually attacks living cells, degenerating tissue and reducing internal organs to dust, it WOULD kill Dante, because there is NO evidence to suggest he can regenerate internal organs.
It really is nothing more than simple logic, and if you really think that not a single thing can kill Dante, then well...Just...Whatever.