Perseus takes this. In Wrath of the Titans he got smashed trough a couple of stone pillars and got punched in the face repeadedly by Ares who is strong enough to lift a fully armored human and toss him like a radgoll and strong enough to break stone with his bare hands. Perseus also fought Acrisius/Calibos who was strong enough to block a fully armored soldiers dropkick without flinching or moving while he was running at him. Acrisius/Calibos was also strong enough to crush a soldiers helmet with ease but when he grabbed Perseus he could't harm him. Perseus also fought a Minotaur who was impaling him with his horn and whatnot. All of that and more.
Along with Perseus durability and strength he also has shown to be fast and agile. When he fought Acrisius/Calibos the second time he was using spinning attacks, backflips and various jumping moves. Perseus also said that he didn't held a sword in his life (first movie) shortly after, Draco wants to train him. Perseus fails the first time and gets knocked down. He gets up and was able to best Draco much to his suprise. Its because he's a Demigod he apperently can learn superfast.
Achilles might be the most skilled fighter but its not gonna help him when Perseus simply overpowers him with his strength and speed, not to mention Perseus has better equipment that Achilles (Lightning Sword, Scorpinoch Shield)
On top of all this he also beheaded Medusa, slayed the Kraken and defeated Kronos.