I have played about 10 games of this and do not believe it can happen without the promo cards.
There is one gladiator that can cause it in the base game:
Defense triples cause one auto-wound to Attacker.
It is REALLY unlikely, but possible.
Edit: actually, no, this couldn't occur - the attacker would have to do at least 3 wounds to kill someone that has 3 defense left, which would mean he would have at least 3 attack (or 2 attack and an axe), which would mean he could not die from the counterattack.