Hmm...this was supposed to be a difficult match-up when I 1st thought it up, cause one is a virus who can absorb Anti-Venom on contact, while the others are two beings who can cure/kill Mercer on contact. But on my way to work today I realized that this fight will either result in Ati-Venom winning or Mercer just barely killing the AV substance before dying himself.
Pretty much its a battle bewteen a virus and an anti-virus. If either touches the other, I'm assuming Mercer will be the most affected negatively. If he succeeds in absorbing AV, it would probably kill him immediately, and AV would win by default since Mercer would have died via the Anti-Venom substance before Mercer could finish off Eddie, thus with Eddie left, AV wins.
Hmph. It was such a difficult make-ya-think battle up til today. I had fun thinking about it.
So Eddie would win. He may lose the "symbiote" in the end, but Mercer will be erradicated/"cured" (killed) one way or the other.