Either low-mid diff for Achilles, Hector was able to kill Ajax and he even push Achilles to mid-high diff(lower end).
Achilles had everything,speed,agile,power and fightskill who make him so op.
Against Hector he wasn´t even exhausted while dancing around, in compare Hector was exhausted. Same with the Beach scene where he kill multiple soldiers without much problems and still was fresh. Proof his stamina/endurance was also very good.