The fear is most likely the one to be killed first, cuz....well he sucks compared with Grey Fox and Vamp is well a vampire and the only thing we've seen him recover from is bullets to his head but we've yet to see him recover from a decapatation.
Grey is the real challange is this fight considering he's fast, but not as fast a Dante though. The very few times Grey has dodged bullet;
1. in Twin snakes, the cutscene when Ocelot gets his arm cut off, there he merely dodges ONE bullet, I've seen Dante evade Lady's gunfire and she's got LOTS of ammo.
2. in Twin snakes again, the cutscene before the bossfight with REX, there he runs from bullets from the REX's railgun. Quite impressive but REX is kind of slow and Grey is kind of fast like Vergil fast.
And Samishe you can dream on and on about Grey and Vamp killing him before he blinks, cuz lets not forget Quicksilver (Dante's total time stopper) cuz with it Dante will slay the vampire, kill the now not-so-fearsome- Fear and our little cyborg can kiss his katana good-bye and that before they even get think one simple thought.
Well I guess that's that then, huh?