Wait a minute, since Kain's a vampire, he's immortal....?! @@;; He did make all the people in that God-forsaken realm into vampires, and made it into Nosgoth. So people turned into = vampires with = NO SOULS. Kain has NO SOUL~~~~!!!! So Raziel can't eat his soul, since he has no soul and he's dead. That was why the Elder God sent Raziel to destroy Kain because he can't eat souls for sustenance~~~!!!!
So Raziel would just have to throw him into a pool of water for a nice bath after centuries of unbathing, really. Raziel WINS~~~!!!!