S'mon said:
Leaving aside Achilles' Damage Reduction from being dipped in the magic river, only 8 mooks can surround him each round, if there's a 2nd rank with longspears (but 1st rank have short weapons) then yes theoretically he can receive a lot of attacks. In practice Achilles can maneuver to keep the number of attacks well short of the theoretical maximum, especially in confined quarters like city streets. And these spear carriers aren't zombies, they're unlikely to maintain morale after the first few dozen have been Great Cleaved in under a minute.
Even a 2e F20 could reliably kill a couple hundred F1 opponents, but at least it'd take him a good while.
Still don't see it. You have our fighter 20 run towards the troop lines which are just under five short bow range increments from the walls (250'). Warrior 1s armed with longspears and short swords run up and surround the F20 at a distance to two squares three ranks deep (40 warriors) with others milling about. 21 W1 archers are within range and fire and do 1d6 damage. Let's say they're onto of the city wall to avoid LOS issues.
Round 1: 1d6 damage
Our F20 steps foward taking 4 AoO and kills the three people in range. W1 repostion around him and get 16 more attacks doing 1d6 damage and 23 archers fire doing 1d6.
Round 2: 3d6 total, 3 dead mooks
Our F20 drops his sword and picks up a longspear off the dead guys and kills 16 and takes a five foot step fo. 8 warriors run up with short swords and attack. Everybody else backs up and forms ranks 3 squares away. 25 archers fire and do 1d6.
Round 3: 4d6 total, 19 dead mooks
Our F20 decides to stop playing around and pulls out his latest WMD, the spiked chain. He kills the 8 guys around him and steps 5' forward. 27 archers fire doing 2d6 damage (including some fractional attacks from earlier).
Round 4: 6d6, 27 dead mooks
Our F20 is now surrounded by mooks 15 ' away two deep. He moves up 10' (225' from wall) and attacks. He kills 8 mooks. 31 archers fire along with 8 AoO for 2 d6 damage.
Round 5: 8d6, 35 dead mooks
Our f20 repeats and kills 8 more and takes 2d6 more damage from 35 archers and 8 AoO and is now 215' from the wall.
Round 6: 10d6, 43 dead mooks
At this point, 10% losses, we could wonder about morale, but I can't find any of the D&D morale rules on the online SRD. Can somebody inform me what they are? Also, can anybody help with the F20 efficiency in killing mooks if they surround him several ranks deep at a distance of 15'? Otherwise, we continue.
Our f20 repeats and kills 8 more and takes 2d6 more damage from 39 archers and 8 AoO and is now 205' from the wall.
Round 7: 12d6, 51 dead mooks
Our f20 repeats and kills 8 more and takes 3d6 more damage from 43 archers and 8 AoO and is now 195' from the wall.
Round 8: 15d6, 59 dead mooks
Our f20 repeats and kills 8 more and takes 3d6 more damage from 47 archers and 8 AoO and is now 185' from the wall.
Round 9: 18d6, 67 dead mooks
Sufficient to say, that at this rate, the F20 dies assaulting the city and we haven't even dealt with how to climb the wall yet. If the mooks position themselves to block his movement and allow the archers to fire, they will win. The F20 needs to move through the mooks, so his option is to ignore the mooks and overrun through them. This is straight F20 strength verus mooks strength or dex. Which unless the F20 has a str of 50, he has a chance of failing, but we'll assume he makes all checks. Even then, he can only take a 30' movement and no attacks. He would clear 30' of the 250' and suffer AoO and archer fire. Which is 28 AoO a round from mooks on ground plus 20 archer attacks plus 12 more ever round. It will take him 8 rounds to reach the wall. That's 660 attacks and 33d6 damage from natural 20's. He is still at the base of the wall.