1.-Hypaspist
Does well vs. infantry, decent against cavalry because of a high hack armor.
2.-Prodromos
Beats cavalry, ok vs. normal infantry.
3.-Peltast
Kills archers, beats anti-infantry infantry units, and with a meathsield it's ok vs. normal infantry.
4.-Huskarl
Does well against archers, ok vs. most infantry and cavalry.
5.-Throwning axeman
I would consider TA a hard counter, in AoM anyways.
6.-Axeman
Does well vs. infantry, decent against cavalry because of a high hack armor.
7.-Slinger
Same as peltast, but when given the sekhmet slinger tech, slingers do well vs. infantry. (meatshield present, of course)
8.-Camel
Does well vs. cavalry, pretty good vs. archers, (most cavalry are good vs. archers) decent against anything else that isn't a cavalry counter.
9.-Katapeltes
Kills cavalry, and because of the high HP it does ok against everything but infantry counters.
10.-Chieroballista
Kills infantry, beats archers, does ok vs. cavalry when it has a meatshield.
11.-Turma
Kills archers, and does ok vs. infantry when it has a meatshield.
AoC hard counter:
Spearman
3 attack
Pretty much useless against everything but cavalry.
This is a hard counter. You really can't say this about ANYTHING in AoM.