Oooooo a good query (and
@Morrus this is definitely a subject we could throw 20 minutes at in a podcast a la
Deadliest Warrior—can we do that please?). I think that fight would depend an awful lot on the circumstances. If Hercules can get in there and grapple Achilles, and keep him in that grapple? He'd crush him. It'd take a while (that Survivor feature would kick in pretty soon and make Achilles a hold out) but if we're talking a field or arena fight, no contest. Take it to somewhere more tactical where Achilles can best use ranged weapons, wriggle away a few times, or maybe slow Hercules down with some minions so he can get a minute to recover, and I'd give Achilles a 1 in 3 shot of walking away from that victorious (but definitely keep my betting money on Herc).